Ingen-Housz, Jan

(b. Breda, Netherlands, 8 December 1730; d. Bowood Park, near Calne, Wiltshire, England, 7 September 1799)

medicine, plant physiology, physics.

Ingen-Housz¹ was the second son of Arnoldus Ingen-Housz and Maria Beckers. His father² was a leather merchant and is also mentioned as having been a pharmacist after 1755. The family was Roman Catholic.

Ingen-Housz was educated at the Breda Latin school where he excelled in classical languages. During the War of the Austrian Succession, British troops were encamped in Terheijden, a nearby village. The physician-general of the British forces, John Pringle, often visited in Breda and became a friend of the Ingen-Housz family. He took a great interest in the bright young Jan and later persuaded him to come to England, where he guided his career.

In the eighteenth century, Catholics in the Netherlands, rather than attend the national universities, preferred the Catholic University of Louvain, from which Ingen-Housz received the M.D. degree summa cum laude on 24 July 1753.³. Probably at the advice of Pringle, he then matriculated at Leiden on 21 December 1754, where he most likely remained no longer than a year. There he continued his medical studies under H. D. Gaubius, a former pupil of Boerhaave and his successor in the chair of medicine and chemistry. He also studied anatomy under B. S. Albinus and physics under van Musschenbroek. He is said to have subsequently studied at Paris and Edinburgh.⁴

Ingen-Housz settled in Breda, where perhaps he had earlier started the family pharmacy.⁵ While living at his father’s house, he established a successful medical practice and began experimenting in physics and chemistry; he probably built his electrostatic machine during this period. Upon his father’s death in 1764 the elder brother Ludovicus inherited the leather business and the pharmacy. Jan used his share of the estate to go to England.

In Edinburgh he became friends with the chemist W. Cullen, the physician A. Dick, and the anatomist A. Monro. He soon moved to Londen and under Pringle’s guidance became acquainted with the anatomists W. Hunter, J. Hunter, the elder A. Monro, and the pediatrician G. Armstrong. He also met Priestley, who was then interested in electricity and optics, and Franklin, who has just then arrived in London. Franklin, especially, became a lifelong friend.

There was at this time a controversy raging in England over Daniel Sutton’s revival of the use of inoculation against smallpox,⁶ despite the charge that such inoculation had in the past proved dangerous and often lethal. It was known that Sutton had a secret regimen and special prescriptions and because his casualties were few, there were physicians who adopted his medical practices. Among them was William Watson, with whom Ingen-Housz worked from 1766 at the Foundling Hospital, where inoculation was mandatory. Watson soon entrusted Ingen-Housz with all inoculations, and in addition to working at other hospitals, Ingen-Housz developed a private inoculation practice. In early 1768 there was a serious smallpox epidemic of the dreaded confluent type in the villages of Berkamstead and Bayford. Ingen-Housz accompanied Thomas Dimsdale, another inoculation proponent, and together they inoculated 700 persons.

In the same year, through a dispute over method, Ingen-Housz’ name became known in his native land. A. Sutherland planned to bring Sutton’s method of inoculation to Holland. When his qualifications were challenged, C. Chais, pastor of the Walloon community in The Hague and author of a book defending inoculation against theological objections,⁷ published a brochure that posed questions, together with answers he had received from Sutherland.⁸ Ingen-Housz thereupon addressed an open letter to Chais in which he defended Dimsdale’s method of inoculation. These brochures spurred an avalanche of pamphlets which led Fagel, secretary of the State General, to ask Ingen-Housz to settle as an inoculator in The Hague.

Ingen-Housz retained his interest in smallpox inoculation until his death and lived to see the introduction of Jenner’s vaccination. He disagreed with Jenner on several points and correponded with him.⁹

In 1768 Ingen-Housz was sent by George III on the advice of a commission¹⁰ to the Austrian court to inoculate the royal family. After successfully inoculating the archdukes Ferdinand and Maximilian and the Therese, Ingen-Housz was showered with gifts and honors. Empress Maria Theresa appointed him court physician with a lifelong annual income of 5,000 gulden. While the empress was disappointed in her hopes that the shy, kind man would develop into an interesting courtier, Ingen- Housz’ use of his financial independence—for research —proved of inestimable value. He traveled throughout the empire, inoculating relatives of the imperial family and practicing teaching inoculation. In January 1771 he went to Paris and then to London, where he was admitted to the Royal Society on 21 March 1771.¹¹ He returned to Vienna in May 1772. In 1775 Ingen-Housz married Agatha Maria Jacquin, the daughter of the famous botanist N. Jacquin; they had no children.

In 1777 and 1778 he was again in Holland and in England, where he delivered the Bakerian lecture before the Royal Society in June 1778. A year later he made his famous experiments on photosynthesis at a country house near London and wrote his book on this subject; it was hurriedly printed in London and Ingen-Housz took copies with him when he returned to Vienna. In July 1780 he was in Paris, where he visited Franklin. Ingen-Housz stayed in Vienna until 1789. He then returned to Paris, arriving on the day the Bastille was stormed. The violence so alarmed him that he immediately left for the Netherlands, and from there returned to England. There is some indication that he actually planned to immigrate to the United States (he had already bought land near Philadelphia), but after Franklin died (17 April 1790) he decided against this move. He remained in London, often staying for long periods at Bowood Par, near Calne, the manor of the marquess of Lansdowne, the former patron of Priestley. It was at Bowood Park that Ingen-Housz died.

Ingen-Housz is most widely known for his discovery of photosynthesis.¹² In the summer of 1771 Priestley had discovered that plants can restore air that has been made unfit for respiration by combustion or putrefaction; that is, by having a candle burn out in it or an animal die in it. (In these early experiments Priestley found only a few cases in which plants did not “improve” the quality of spoiled air; in his experiments of 1779, however, he found many such cases.) Some investigators outside of England, notably the Swedish chemist C. W. Scheele, were unable to confirm Priestley’s observations. Others, and particularly the Dutch chemists J. R. Deiman and Paets van Troostwijk, were more fortunate. Theywere the first to use the eudiometric method in research on photosynthesis, and Ingen-Housz must have been familiar with their work.

Since there is no evidence that Ingen-Housz had worked on photosynthesis previously, it must have been Priestley’s publications on the subject that motivated his own investigations.¹³ the book in which Ingen-Housz reported his results, Experiments Upon Vegetables, Discovering Their Great Power of Purifying the Common Air in the Sunshine and of Injuring it in the Shade and at Night, advanced the understanding of the phenomenon considerably. He established that only the green parts of a plant can “restore” the air, that they do this only when illuminated by sunlight, and that the active part of the sun’s radiation is in the visible light and not in the heat radiation. In addition he found that plants, like animals, exhibit respiration, that respiration continues day and night, and that all patts of the plant—green as well as nongreen, flowers and fruit as well as roots—take part in the process.

Felice Fontana had found that during respiration animals produce fixed air (Co₂), and Ingen-Housz determined that plant respiration produces the same gas. He proved these and several less important points through a series of well-designed experiments. His results also explained why Scheele’s and some of Priestley’s experiment had failed. (It is interesting to note that Priestley’s failures in 1771 occurred during the dark month of December.)

In the years that followed, partly inspired by controversies with Priestley and Senebier, Ingen-Housz continued to study plant assimilation and respiration. He knew the amount of dephlogisticated air (oxygen) consumed by plants through respiration to be far smaller than the amount of the gas produced through photosynthesis. This finding led him to believe that plants and animals mutually support each other, the animals consuming dephlogisticated air and producing fixed air, the plants doing exactly the reverse. He also felt that the phenomenon of photosynthesis would enable scientists to establish the demarcation between plants and animals of the lower forms of life.

Because of their attacks on Ingen-Housz, Priestley and Senebier are often given credit for the discovery of photosynthesis. But it is beyond doubt that neither of the two had even a vague understanding of this process before the publication of Ingen-Housz’ book in 1779; even in their later writings the process is not entirely clear. Therefore the discovery of both photosynthesis and plant respiration belongs to Ingen- Housz alone.

During this period Ingen-housz met Sir John Sinclair, president of the Board of Agriculture, who encouraged his studies of plant nutrition. The chemistry of plant growth was not yet understood, especially the origin of carbon in plants. The French chemist Hassenfratz had proposed the theory that the carbon was taken up from the soil by the roots of the plants, the so-called humus theory; the humus, decayed remains of animals and plants in the soil, being the storehouse of the carbon. In a contribution intended for publication by the Board of Agriculture, “on the Food of Plants and the Renovation of Soils,” Ingen- Housz declared that carbon dioxide in air is the source of carbon in plants, thus explaining the disappearance of the gas and the production of oxygen in photosynthesis.

The work on photosynthesis had given Ingen-Housz an understanding of the influence of air quality on the performance of organisms. As a physician he conjectured that respiratory ailments could be relieved if purer air could be administered. He consequently devised an apparatus to produce and administer to the patient pure, dephlogisticated air. Although there is no evidence that he employed this respiratory treatment himself, others soon followed his suggestion. Ingen-Housz can thus be credited with the initiation of oxygen therapy.

Ingen-Housz’ interest in photosynthesis may well have derived from his interest in the chemistry of gases. He was especially interested in “inflammable air,” at the time the name for combustible gases. He experimented with explosive gas mixtures and used a mixture of air and ethyl ether vapor as the propellant for a pistol, which was fired electrically. He also studied the production of dephlogisticated air from metal oxides, and was the first to try the demonstration -experiment of burning a steel wire in pure oxygen.¹⁴ To replace the cumbersome tinderbox, he designed a hydrogen-fueled, electrically ignited lighter, and he substantially improved the phosphor matches invented by Peibla (1781).

Ingen-Housz’ earliest scientific interest was in the field of physics, especially electricity. He was the first to use disks instead of revolving cylinders or globes in electrostatic generators.¹⁵ In the Bakerian Lecture of 1778, he explained the phenomena of Volta’s electrophore by means of Franklin’s theory of positive and negative electricity, a crucial demonstration of the correctness of Franklin’s view. he also entered the controversy on blunt lightning rods (advocated by Wilson) versus pointed ones (advocated by Franklin). While living in Austria, he often advised the government on the placement of lightning rods on powder houses. He experimentally refuted the statement that plant growth is promoted by electricity.

In the field of magnetism, Ingen-Housz experimented with artificial magnets, made according to the ideas of Gowin Knight, and devised methods of dampening the vibrations of magnetic needles. He also discovered the paramagnetism of platinum.

Ingen-Housz’ research on algae led to three other significant contributions. Although he could not identify the “green matter” that Priestley spoke of (1779), he discovered its swarm spores, and his investigation prompted him to suggest the use of the very thin glass resulting from glassblowing operations as cover plates for liquid microscopic preparations, which greatly facilitated observation. But perhaps the most important consequence of his algae research was his discovery and correct description of Brownian motion.

Brown, in his discovery paper of 1827, had himself suggested the names of some possible precursors; but an examination of their work has shown that none of these scientists was aware that lifeless particles might show the motion.¹⁶ Ingen-Housz demonstrated that finely powdered charcoal suspended in alcohol shows the irregular motion, just as minute organisms such as Infusoria will.¹⁷ Although Ingen-Housz has not been properly credited with this discovery, his name did become associated with an experiment that Franklin inspired, the demonstration of the difference of heat conductivity of different metals. Ingen-Housz carried out Franklin’s ideas and obtained correct, although only qualitative, results.¹⁸

NOTES

1. Ingen-Housz himself used this form of the name (although he sometimes signed his letters with Housz only) and was so referred to by his contemporaries. Descendants of Ingen- Housz’ older brother Ludovicus usually write the name without the hyphen.

2. On Arnoldus and Ludovicus Ingen-Housz see G. J. Rehm, De Bredasche apothekars van de 15e tot het begin van de 19e eeuw (Breda, 1961), pp. 84-90.

3. Although biographers have generally stated that Ingen- Housz started his studies at Louvain in 1746, this is unlikely since the town was under enemy occupation after May 1746. It is probable that he did not go to Louvain before the autumn of 1748. The earliest matriculation record of Ingen-Housz falls between August 1750 and February 1751, allowing for only three years to obtain his medical degree. A printed dissertation is not known; Ingen-Housz was probably promoted after the defense of propositions. A broadside poem in Latin, issued at his promotion, established the date. A facsimile of this poem is reproduced by H. S. Reed, facing p. 31.

4. V. Flint, p. 9, states that she has a letter from the University of Edinburgh which confirms that Ingen-Housz was there between 1755 and 1757 but did not matriculate. He probably attended a privatissimum of W. Cullen.

5. Because, in Breda, an M.D. had the right to dispense prescriptions, it is logical to assume that the pharmacy was operated under the authority of Jan Ingen-Housz, rather than his father, who would have had to go through a four- year apprenticeship.

6. Inoculation consisted of introducing the live virus of the disease under the skin of the patient and must be distinguished from vaccination, introduced later by Jenner (1798).

7. C. Chais, Essai apologétique sur la méthode de communiquer la petire vérole par inoculation (The Hague, 1754).

8. C. Chais, Lettre . . . à Mr. Sutherland . . . sur la nouvelle méthode d’inoculer la petite vérole (The Hague, 1786).

9. See P. W. van der Pas, “the Ingen-Housz-Jenner Correspondence”.

10. Oordeel van de genees—en heelmeesters van den koning van Engeland aangaande de manier van inentinge der kinderpokjes der heeren Suttoniaanen (The Hague, 1767).

11. Ingen-Housz had been elected a fellow of the Royal Society on 25 May 1769.

12. In this brief discussion of Ingen-Housz’ work, the old chemical nomenclature is used as it appeared in his papers and books on photosynthesis. It is not certain whether Ingen-Housz agreed with lavoisier’s views on phlogiston, but on 5 January 1788 he wrote a letter to J. H. Hassenfratz to thank him for “I’exemplaire de la nouvelle nomenclature chimique, que je n’approuve pas”.

13. It would seem from a letter to Franklin dated 25 May 1779 (see I. M. Hays, Calendar of the Franklin Paper, II, 38) that Ingen-Housz had originally intended to retire to the country to finish his book on smallpox, which was never completed.

14. E. Cohen, “Wie heeft de verbranding van een horlogeveer in zuurstof het eerst uitgevoerd?”, in Chemisch weekblad, 8 (1911), 87-92.

15. In the 1st ed. (1767) of The History and Present State of Electricity, Priestley attributed this invention to J. Ramsden; in the 2nd ed. (1769) he credits Ingen-Housz, who must have convinced him of his priority. Ingen-Housz’ machine was still a friction and not an induction machine, which was the forerunner of the modern high-voltage electrostatic generators.

16. P. W. van der Pas, “The Early History of the Brownian Motion”, in proceedings. Twelfth International Congress of the History of Science and Technology (August 1968), Actes XII^e Congrès International d’Histoire des Sciences (Paris, 1968), VIII, 143-158.

17. See P. W. van der Pas, “The Discovery of the Brownian Motion”.

18. Max Jacob, Heat Transfer, 2 vols (New York, 1949), 1 207-209, gives the mathematical theory of the experiment.

BIBLIOGRAPHY

I. Manuscripts. Wiesner (see below) mentions many letters and other personal writings preserved at various institutions. In addition he presents abstracts of documents concerning Ingen-housz, preserved in a number of Austrian archives.

II. Original Works. As Wiesner’s bibliography, while having few omissions, is wanting in accuracy, a complete bibliography is given here in the hope of providing more correct information; only the primary references are included.

(1)“Extract of a Letter From Dr. J. Ingenhousz to Sir John Pringle, Bart., PRS, Containing Some Experiments on the Torpedo, Made at Leghorn, January 1, 1773 (After Having Been Informed of Those by Mr. Walsh). Dated Salzburg, March 27, 1773”, in philosophical Transactions of the Royal Society, 65 (1775), 1-4.

(2)“Easy Methods of Measuring the Diminution of Bulk, Taking Place on the Mixture of Common Air and Nitrous Air, With Experiments on Platina”, ibid., 66 (1776), 257-267.

(3)“A Ready Way of Lighting a Candle, by a Very Moderate Electric Spark”, ibid., 68 (1778), 1022-1026.

(4)“Electrical Experiments, to Explain How Far the Phenomena of the Electrophorus May Be Accounted for by Dr. Franklin’s Theory of positive and Negative Electricity, Being the Annual Lecture, instituted by the Will of Henri Baker, Esq., FRS” ibid., 1027-1048.

(5)“Account of a New kind of Inflammable Air or Gas, which Can Be Made in a Moment Without Apparatus, and is as Fit for Explosion as Other Inflammable Gases in use for That Purpose; With a new Theory of Gun Powder”, ibid., 69 (1779), 376-418.

(6)“On Some New Methods of Suspending Magnetic Needles”, ibid., 537-546.

(7)“Improvements in Electricity”, ibid., 659-673.

(8)“On the Degree of Salubrity of the Common Air at Sea, Compared With That of the Sea-shore and That of Places, Far Removed From the Sea,”, ibid., 70 (1780), 354-377.

(9)“Exposition de plusieurs lois qui paroissent s’observer constament dans les divers mouvements du fluide électrique et auxquelles les physiciens n’avoient pas fait une suffisante attention”, in journal de physique théorique et appliquée, 16 (1780), 117-126.

(10)“Uitslag der proefnemingen op de planten, strekkende ter ontdekking van derzelver zonderlinge eigenschap om de gemeene lucht te zuiveren op plaatsen waar de zon schijnt, en dezelve te bederven in de schaduwe en gedurende den nacht”, in Algemeene Vaderlandsche Letter-oefeningen, 2 (1780), 247-249.

(11)“Verhandeling over de gedephlogisteerde lucht en de manier hoe men dezelve kan bekomen en tot de ademhaling kan doen dienen“, in Verhandelingen Bataafsch genootschap der proefondervindelijke wijbegeerte te Rotterdam, 6 (1781), 107-160.

(12)“Some Farther Considerations on the Influence of the Vegetable Kingdom on the Animal Creation”, in philisophical Transaction of the Royal Society, 72 (1782), 426-439.

(13)“Observations sur la vertu de l’eau impregnée d’air fixe, de differens acides et de plusieurs autres substances, pour en obtenir par le moyen des plantes et de la lumiére du soleil de l’air déphlogistiqué”, in journal de physique théorique et appliquée, 24 (1784), 337-348.

(14)“Réflexions sur l’économie des végétaux”, ibid., 443-455.

(15)“Remarques sur l’origine et la nature de la matière verte de M. Priestley, sur la production de l’air déphlogistiqué par le moyen de cette manière et sur le changement de l’eau en air dèphlogistique”, ibid., 25 (1784), 3-12.

(16)“Remarques de M. Ingen Housz sur la lettre précédente avec quelques observations ultérieurs sur la vertu de l’eau impregnée d’air fixe”, ibid., 78-91, reply to a letter of Senebier (see below).

(17)“Lettre de M. Ingen Housz á M. Jan van Breda au sujet de la quantité d’air déphlogistiqué que les végétaux répandent pendant le jour; au sujet des raisons de l’inexactitude de la quantité d’air déphlogistiqué qu’on otient par les végétaux, exposés au soleil dans l’eau imbibée d’air fixe, ainsi que sur la véritbale cause de l’influence méphitique nocture des végétaux dans l’air,” ibid., 437-450.

(18)“Observations sur la construction et l’usage de l’eudiomètre de M. Fontana et sur quelques propriétés particulières de l’air nitreux, adressé à M. Dominique Beck . . .,”., 26 (1785), 339-359.

(19)“Lettre de M. Ingen Housz à M. N. C. Molitor, . . .au sujet de l’effet particulier qui ont sur la germination des sémences et sur l’accroissement des plantes formés, les differentes espèces d’airs, les differens degrés de lumière et de la chaleur et de I’èlectricité,” ibid., 28 (1786), 81-92.

(20)“Lettre de M. Ingen Housz . . . à M. Molitor . . . au sujet de l’influence de l’électricité atmospérique sur les végétaux,” ibid., 32 (1788), 321-337.

(21)“Lettre de M. Ingen Housz à M. de la Métherie sur les métaux comme conducteurs de la chaleur,” ibid., 34 (1789), 68-69.

(22)“Expériences qui prouvent: 1^e, que les plantes évaporent une quantité plus grande d’air vital pendant le jour à l’air libre que nous en voyons répandre étant couvert d’eau pure; 2^e, que leur évaporation nocturne d’un air méphitique, qui est très petite lorsq’elles sont couvertes d’eau et très considerable dans l’état naturel, qu’il y a un mouvement et déplacement continuel du fluide aerien dans les végétaux,” ibid., 436-446.

(23)“Aqua mephitica alcalina of loogzoutig luchtzuur water, een nieuw ontdekt en uitmuntend geneesmiddel in het graveel en den steen,” in Scheikundige Bibliotheek, 1 no. 1 (1792), 41; no. 2, 95; no. 3, 175.

(24)“Brief aan Jan van Breda, behelzende eenige proeven met wormdoodende vogten genomen,” ibid., 2 (1794), 153.

Of the following books by Ingen-Housz, some are collections of his papers, but in most cases these reprints are considerably modified:

(25)Lettre de Monsieur Ingenhousz, Docteur en médecine à Monsieur Chais, Pasteur de l’église Wallone de la Haye, au sujet d’un brochure contenant sa lettre à M. Sutherland, et une réponse de M. Sutherland à M. Chais, sur la nouvelle méthode d’inoculer la petite vérole (Amsterdam, 1768).

(26)Nova, tuta, facilisque methodus curandi calculum, scorbutum, podagram, destruendique vermes in humano corpore nidulantes. Ci addita est methodus extemporanea impregnandi aquam aliosque liquores aëre fixo etc. Latno sermone ab J. Ingenhousz (Leiden, 1778; 2nd ed., Louvain, 1797), Latin trans. of a book by N. Hulme (see below), with appended notice by Ingen-Housz on the use of carbonated water; Dutch trans., Nieuwe, veilige en gemakkelijke manier om den steen . . . (Rotterdam, 17780; German trans., Neue, sichere Methode der Heilung des Steins. . .(Vienna, 1781).

(27)The Baker Lecture for Year 1778, Read at the Royal Society, June 4, 1778. Experiments on the Electrophorus (London, 1779); Dutch trans., Proeve over den electrophorus. . . (Delft, 1780); German trans., Anfangsgründe der Elektrizität (1781).

(28)Experiments Upon Vegetables Discovering Their Great Power of Purifying the Common Air in the Sunshine and of Injuring it in the Shade and at Night, to Which is Joined, a new Method of Examining the Accurated Degree of Salubrity of the Atmosphere (London, 1779); Dutch trans., Proeven op plantgewassen . . . (Delft, 1780), a promised second vol. never having been published; French trans., Expériences sur les végétaux . . . (Paris, 1780); nd ed. (1785), see G. A. Pritzel, Thesaurus literatuae botanicae (Milan, 1871; repr. 1950), o. 4435; 3rd ed., 2 vols.: I (Paris, 1787); II (Paris, 1789); no evidence of a third vol., which is sometimes mentioned, has been found; German trans., Versuche mit Pflanzen, wodurch entdeckt worden dasz sie die Kraft besitzen, die atmosphärische Luft beim Sonnenschein zu reinigen, und im Schatten und des Nachtsüber zu verderben (Leipzig, 1780); 2nd ed., 3 vols. (Vienna, 1784-1790), the best and most complete ed.

(29)Nouvelles expériences et observations sur divers objets de physique, 2 vols.: I (Paris, 1785); II (Paris, 1789); German trans., Vermischte Schriften physisch-medizinischen Inhalts . . . nebst einigen Bemerkungen über den Einfluss der Pflanzen auf das Tierreich (Vienna, 1782); 2nd ed., 2 vols.: I (Vienna, 1785); II (Vienna, 1784 [sic]); Dutch trans., Verzameling van verhandelingen over verschillende natuurkundige onderwepen, 2 volts.: I (The Hague, 1784);II (The Hague, 1785).

(30)Epistola ad J. A. Scherer (Vienna, 1794).

(31)Miscellana phyisco-medica (Vienna, 1795).

(32)Additional Appendix to the Outlines of the Fifteenth Chapter of the Proposed General Report From the Board of Agriculture; On the Subject of Manures (London, 1796).

(33)An Essay on the Food of Plants and the Renovation of Soils (n.p., 1796); Dutch trans., Proeve over het voedsel der planten en de vrugtbaarmaking van landerijen (Delft, 1796); German trans., Ueber die Ernährung der Pflanzen und Fruchtbarkeit des Bodens (Leipzig, 1798).

III. Secondary Literature. The following items are from the contemporary literature which pertains to Ingen- Housz:

(34)N. Hulme, A Safe and Easy Remedy Proposed for the Relief of the Stone, the Scurvy, Gout, etc., and for the Destruction of Worms in the Human Body . . . Together With an Extemporaneous Method of Impregnating Water - With Fixed Air (London, 1778).

(35)W. Henley, “Observations and Experiences, Tending to Confirm Dr. Ingen Housz’ Theory of the Electrophorus and to Show the Impermeability of Glass to the Electric Fluid,’ in Philosophical Transactions of the Royal Society, 68 (1778), 1049-1058.

(36)J. Senebier, “Mémoire sur la metière verte, ou plutôt sur l’espéce de Conserve, qui croit dans les vaisseaux pleins d’eau exposés à l’air et sur l’influence singuliére de la lumiére pour la déveloper, in Journal de physique théorique et appliquée, 17 (1781), 209-216..

(37)“Lettre de M. Senebier à M. Ingen Housz, (sur ses observations sur l’eau impregnée d’air fixe, et de differens acides),” ibid., 25 (1784), 76-77..

(38)B. Franklin, “A Letter From Dr. B. Franklin to Dr. Ingenhausz . . . (Throughts Upon the Construction and Use of Chimneys),” in Transactions of the American Philosophical Society, 2 (1786), 1-27.

(39)“Lettre de M. Fontana au célèbre M. Ingen Housz . . .sur la décomposition de l’eau,” in Journal de phsysique théorique et appliquée, 28 (1786), 310-315..

(40)“Lettre à M. Ingen Housz sur la décomposition de l’eau, par M. Adet,” ibid., 436-441..

(41)M. de la Métherie, “Réflexions sur la lettre précé- dente de M. Adet, relativement à la décomposition de l’eau,” ibid., 28 (1786), 442-446..

(42)“Effets de l’électricité sur les plantes, Réflexions ultérieurs sur le contenu du mémoire de M. Ingen Housz,” ibid., 35 (1789), 81-83..

(43)“Lettre de M. van Marum à Jean Ingen Housz, . . . contenant la description d’une machine électrique, construite d’une maniére nouvelle et simple et qui rèunit plusieurs advantages sur la construction ordinaire,” ibid., 38 (1791), 447-459..

(44)“Seconde lettre de M. van Marum à M. Jean Ingen Housz, . . . contenant quelques expériences et des considérations sur l’action des vaisseaux des plantes qui produit l’ascension et le mouvement de leur séve,” ibid., 41 (1792), 214-220..

(45)“Lettre de A. F. Humboldt à Ingen Housz sur l’absorption de l’oxygène par les terres,” ibid., 47 (1795), 377-378.

The following writings are of interest for data on the life of Ingen-Housz:

(46)M. J. Godefroi, “Het leven van Dr. Jan Ingen- Housz, geheimraad en lijifarts van Z. M. Keizer Josef II van Oostenrijk,” in Handelingen van het Provincial Genootschap van Kunsten en Wetenschappen in Noord Brabant (’s Hertogenbosch, 1875)..

(47)M. Treub, “Jan Ingen-Housz,” in De Gids, 18 (1880), 478-500..

(48)H. W. Heinsius, “Jan Ingen-Housz,” in Album der Natuur, 46 (1897), 1-15..

(49)J. Wiesner, Jan Ingen-Housz, sein Leben und sein Wirken als Naturforscher und arzt (Vienna, 1905), the best biography of Ingen-Housz..

(50)E. Mortreux, “Johannes Ingen-Housz,” in Nieuw Nederlandsch Biografisch woordenboek, 6 (1912), 832-837..

(51)H. S. Reed, “Jan Ingen-Housz, Plant Physiologist. With a History of the Discovery of Photosynthesis,” in Chronica botanica, 11 (1950), 285-396..

(52)Dictionary of National Biography, 10 (1903), 433..

(53)M. Speter, “Jan Ingenhousz’ ‘verbessertes’sauerstoff Inhalierungs Apparat (1783-84) und dessen Ausgestaltung durch Paskal Joseph Ferro,” in Wissenschaftliche Mitteilungen des Drägerwerks, no. 5 (1936)..

(54)Vera Flint, “The Botanical Studies of Jan Ingen- Housz and the Influence of his Work on his Contemporaries and Successors,” diss. (Univ. of London, 1950)..

(55)P. W. van der Pas, “The Ingenhousz-Jenner Correspondence,” in Proceedings. Tenth International Congress of History of Science and Technology (1964), 957-960; also in Janus, 51 (1964), 202-220, more complete..

(56)P. W. van der Pas, “The Discovery of the Brownian Motion,” in Scientiarium historia, 13 (1971), 27-35.

P. W. van der Pas