ON TllK VITALISTIC VIKW OF NATIKb:. 417 



of intensity the living processes common to all. Just 

 so a state or human society is made up of a large 

 numl)er of individuals, all having the same human 

 nature, who carry on the different functions peculiar 

 to each with varying degrees of efficiency. The concep- 3o. 



^. . , „ , . -^ '- The cellular 



tion or the cell as the unit or type of all living H'wry. 

 matter, and the further discovery that there exist uni- 

 cellular beings which are not essentially different from 

 the constituent living elements of the most complicated 

 organisms, has brought physiological research to a focus. 

 The difficulties in the study of biological phenomena 

 have vanished as those of the organic chemist did on 

 the introduction of the conception of valency, of the 

 saturating powers of chemical substances. Accordingly, 

 if we compare a text-book of these subjects written in 

 the middle of the century with one Ijelonging to the 

 latter part of it, we find an enormous difference of 

 treatment. It is instructive to contrast the introduction 

 given in Johannes ]\Iiiller's ' Elements of Physiology ' 

 and that of Professor Michael Foster's ' Text-book.' The 

 former represents the most advanced knowledge obtain- 

 able at the end of the thirties — the latter that of a 

 generation later. The former contains a lengthy intro- 

 duction on general physiology — the latter a short one 

 on the physiological properties of a living amoeba,^ a 



' Already, in 1835, K. E. vou 

 Baer pointed out how tlie study 

 of one small animal can revolution- 

 ise our entire reasoning. " Ninety 

 years ago a naturalist discovers 

 the hydropolyp, an insignificant 

 slimy animal, not larger than a 

 peppercorn, and how, without 

 head, sense-organs, muscles, nerves, 

 blood, and sexual organs it never- 



theless is nourished, grows, feels, 

 moves, and multiplies, — how it can 

 even be divided, each part form- 

 ing a whole : he observes it with 

 much wonder for nine years with 

 untiring perseverance. At that 

 time many would, no doubt, con- 

 sider such an occupation childisii 

 and unworthy, yet these diligent 

 observations have slowlv but ma- 



VOL. II. 2 D 



