186 



DISCOVERY 



in the outer world of matter, namely, the evolution 

 of the conception of the molecule. The atom as Dalton 

 conceived it in 1804 was the smallest portion of matter 

 which could enter into chemical union with some other 

 similar substance, or could replace some other atom in 

 a compound, thus forming a new compound. In 

 course of time the Italian chemist Count Amedeo 

 Avogadro (1776-1856) became convinced that there 

 must be bodies composed of two, three, or more atoms 

 — compound atoms, in fact — which were able to exist 

 in a state of freedom, in gases for instance. Avogadro 

 therefore coined in 1811 the word "molecule" (the 

 diminutive of the Latin moles = a mass) " as a term 

 of convenience " to express the conception he had of 

 the smallest portion of matter able to exist in a free 

 state. 



Dalton 's atom is the unit of chemical activity, 

 Avogadro 's molecule is the unit of physical structure. 

 For many a day after Avogadro's time, the atom and 

 the molecule were still "terms of convenience": 

 neither had been seen ; but to-day both atoms and 

 molecules are believed in as real existences ; and as 

 for molecules, they have been weighed and measitred. 



The author of a recent textbook of chemistry writes 

 thus : " The Brownian movement has revealed to us 

 bodies intermediate between ordinary particles and 

 single molecules, and has enabled us to estimate the 

 actual weight of molecules. . . . There is thus no 

 question that molecules and atoms are real." Not 

 only so, but the physical chemist can calculate the 

 number of molecules in a given volttme of gas. Thus 

 the conception of the molecule has been discovered to 

 correspond to a real, external, physical entity. 



Fermentation and Digestion 



No better example than that of the ferments could 

 be given of a notion becoming in course of time a 

 substance isolated and tangible. Fermentation, the 

 totality of changes produced indigestible, coagulable, 

 or putrescible material, was for ages believed to be 

 inscrutably mysterious. It was made the subject of 

 debate between the iatro-mathematicians and the 

 iatro-chemists of the seventeenth century, but neither 

 school really understood it. 



Digestion, the great fermentative process in animals, 

 was confused not only with putrefaction, but with 

 boiling and with the effervescence of gas in chemical 

 operations. Stahl (1660-1734) saw in digestion the 

 direct activity of the soul or anima which, he held, 

 permeated every tissue and endowed it with its special 

 powers. The chemistry of it all, however, was un- 

 known ; the very conception of a ferment, a substance 

 produced by living matter but not itself living, had 

 not as yet emerged from the mental confusion. 



Van Helmont (1577-1644), Sylvius (1614-1672), de 



Graaf (1641-1672), and Haller (1708-1777) all groped 

 for it, but it was not until the work of Rene Antoine 

 Ferchault de Reaumur about 1750 that any true notion 

 was held as to digestion being a form of fermentation. 

 Reaumur was the first to obtain gastric juice in an 

 approximately pure state and to attempt digestion 

 with it outside the body. Spallanzani, the distin- 

 guished Italian naturalist at Pavia, began where 

 Reaumur left off, and discovered in 1777 that digestion 

 was by no means putrefactive, but was apparently 

 due to some " solvent power "or " active principle of 

 solution " in the gastric juice. Then, by degrees, 

 as physiological chemistry improved its methods it 

 obtained finer results, and at last " the solvent power " 

 or "principle of solution" in the gastric juice was 

 isolated in 1862 as the white powder, pepsin, a name 

 which had been given by Schwann to the " active 

 principle " as far back as 1836. Soon other ferm_ents 

 were either isolated or obtained in solution, and to-day 

 in our laboratories we store in glass bottles a dozen • 

 or more of those actual substances which are the modern : 

 representatives of the ' ' principles of solution ' ' of the 

 early researchers. The vague has become definite, the 

 conceptual power or property has become the material < 



substance or entity. 1 



I 



Diseases of the Thyroid and Pituitary Glands 



The story of the isolation of the internal secretion of 

 the thyroid gland — the body covering the projection 

 in the throat called " Adam's apple " — is very similar. 

 Physicians had come to learn that if this gland was in 

 a state of inactivity in early life the condition of im- 

 becility or cretinism was the result, and if the gland 

 became inactive in later life a curious disease called 

 myxoedema was produced. In this latter condition 

 the skin was tumified and the brain showed degenera- 

 ti\'e changes which were reflected in the loss of energy 

 and in the general lethargy of the patient. 



It was also believed that, when the thvToid gland 

 became over-active, a distressing disease, exoph- 

 thalmic goitre, characterised bj^ a rapid heart-heat, 

 was the result. In course of time it was discovered 

 that cretinism and myxcedema were both ameliorated 

 or cured by administration of thyroid gland ; and, on 

 the other hand, exophthalmic goitre was relieved by 

 excision of a portion of the thyroid. An internal secre- 

 tion was assinued to be absent or greatly diminished 

 in cretinism and myxoedema, but increased in exoph- 

 thalmos. In due time, at the close of 1914, a soluble, 

 stable, crystalline substance named thyroxin was 

 isolated and found to do everything that thyroid gland 

 itself would do. Three and a half tons of pigs' thyroid, 

 have been made to yield only 36 grammes of the 

 hormone thyroxin. Another surmise had been materia- 

 lised, incarnated, objectified. 



