August 29, 1901J 



NA TURE 



419 



first adequate description of the changes undergone by 

 the developing chick in ovo. He described the capillary 

 circulation, and thus completed the immortal discovery 

 of Harvey, and although not the first to observe the 

 corpuscles of the blood, for he was anticipated in this 

 by a few years by Swammerdam, his observation was 

 independent of Swammerdam's, and made long prior to 

 its publication. The extent of his researches into the 

 structure of the tissues and organs is testified to by the 

 number of parts to which his name is attached, e.g. the 

 Malpighian tubules of insects, the rete Malpighii of the 

 epidermis, the Malpighian bodies of the spleen and 

 kidney. " Whatever part of natural knowledge he 

 touched he left his mark ; he found paths crooked and 

 he left them straight ; he found darkness and he left 

 light." 



The effect upon physiology of the new knowledge of 

 chemistry which was dawning in the seventeenth century, 

 as the result, in large measure, of the work of van 

 Helmont (i 577-1644), mystic though he was in many 

 matters, and of his immediate successors, is dealt with in 

 the fifth and sixth lectures. Practising as a physician, van 

 Helmont was nevertheless mainly occupied, at Vilvorde 

 in Belgium, with carrying out chemical observations and 

 experiments. Although he received the Elijah cloak of 

 Paracelsus, whose spiritualistic doctrines he adopts and 

 even develops, and although he was still imbued with 

 the Galenic doctrines, in spite of the fact that Harvey's 

 work was already published when he wrote and must 

 have been known to him, he nevertheless shows himself 

 to be 



" a patient, careful, exact observer . . . who watches, 

 measures and weighs, who takes advantage of the aid 

 of instruments of exact research, who reaches a conclu- 

 sion by means of accurate quantitative estimations. . . . 

 Throughout the whole of his writings is seen the con- 

 tinued endeavour to weave his exact chemical physical 

 knowledge and his spiritualistic views into a consistent 

 whole. . . . These two sides of van Helmont's character 

 are not unfitly indicated by the two words gas and bias, 

 'two new terms,' he himself says, 'introduced by me 

 because a knowledge of them {i.e. of the things they 

 indicate) was hidden from the ancients.' By ' bias ' he 

 meant an invisible spiritual agency which directs and 

 governs material changes : this is the archeus of Para- 

 celsus. By '' gas^ he clearly meant what we now call 

 carbonic acid gas. ... He gives it that name because 

 the sound is not so far from that of ' chaos,' the un- 

 formed womb of all things." 



He shows that gas is produced by the combustion of 

 charcoal, by the fermentation of fruits, by the ignition of 

 gunpowder. He gives an account of digestion, which he 

 likens to fermentation. He recognises the essentially 

 acid nature of the gastric secretion and its chemical 

 action upon food. He describes absorption from the 

 intestines as being due, in part at least, to diffusion. 

 But he does not grasp the idea of the use of air in 

 breathing ; he still clings to the old notion of " vital 

 spirits." He anticipates modern physiology in teaching 

 that the tissues prepare their own substance independently 

 from the blood. But, to judge by his writings, van Hel- 

 mont was at heart more pleased with his bias than with 

 his gas. '' He allows to man alone a sensitive soul. The 

 throne of this soul is in the pylorus ; ' there it sits and 

 there it abides all life long.' He gives reasons for this 

 NO. 1 66 1, VOL. 64] 



conclusion, e.g. a great emotion is felt at the pit of the 

 stomach ; a severe blow in the pit of the stomach will stop 

 the heart." 



Van Helmont was followed by Franciscus Sylvius 

 (1614-1672) in explaining many of the phenomena of the 

 body by the help of chemical science, and by Regner de 

 Graaf (1641-1673) in his observations upon digestion. 

 De Graaf was the first to obtain pancreatic juice, saliva, 

 and bile from artificial fistuhe ; his methods are used at 

 the present day. And soon afterwards the knowledge of 

 glands and their functions was still further advanced by 

 the discoveries of Peyer (1653-1712), and von Brunner 

 (1653-1727), of the glands in the intestine now known by 

 their names. 



But the progress of chemical science was destined to 

 be arrested for many years by the speculations and 

 teaching of George Ernest Stahl (1660-1734), who was 

 successively court physician at Weimar, professor of 

 medicine at Halle, and physician to the King of Prussia. 

 "He was an accomplished chemist, and his name must 

 always be borne in mind in dealing with the history 

 of science, if for nothing else, for the reason that he was 

 the author of the famous theory of phlogiston, which 

 ruled with a rod of iron, as it were, the thoughts of 

 natural philosophers for a hundred years." 



Stahl maintained the view that the chemical changes of 

 the living body were entirely different from those of the 

 laboratory, that they were directly governed by the 

 sensitive soul, which pervaded all parts, which not only 

 set the chemical agent in motion, but was itself the 

 agent. " He thus stands forth at the close of the seven- 

 teenth century as the founder of 'animism,'" a doctrine 

 which, under the name of a vital principle, maintained 

 itself through the succeeding centuries, and e.xists in a 

 modified form even at the present day. 



The seventh lecture of the series, which is devoted to 

 the English school of the seventeenth century and deals 

 mainly with the evolution of the physiology of respiration, 

 is one of great interest, bound up as it is with the early 

 history of the Royal Society. The fundamental experi- 

 ment that a candle goes out, an animal dies, in a space 

 deprived of air is due to Robert Boyle (1660). Robert 

 Hook in 1667 showed the Fellows of the Royal Society 

 that an animal can be kept alive by artificial respiration 

 without any movement of the lung or chest wall ; that 

 the air alone, coming in contact with the blood, is the 

 essential part of respiration. Richard Lower(i63i-i69o), 

 besides his well-known work on transfusion and on the 

 structure and action of the heart, also carried the subject 

 of the physiology of respiration still further by showing 

 that the change of the blood from venous to arterial is 

 merely a change of colour due to air ; he concluded that 

 this entrance of fresh air into the blood is as necessary 

 for the body as for the combustion of fuel. But it was 

 left for John Mayow (1643- 1679) 'o prove that it is a part 

 only of the air to which this property is due, and to this 

 part he gave the name of " nitro-aereal or igneo-aereal " 

 spirit, which was neither more nor less than that which 

 we now term oxygen. This was before .Stahl had intro- 

 duced the phlogiston theory, the essence of which was 

 that when a combustible body was burned, phlogiston 

 departed from it : it lost weight. Mayow is quite 

 e.xplicit on this point, showing that when antitnonium is 



