Physiology of Animals. 51 



gestion was adopted and elaborated by Schwendener, 

 and its correctness was further demonstrated by Bornet, 

 Stahl, and others. In spite of the opposition of many 

 eminent lichenologists, the "dual hypothesis" has now 

 general recognition. 



Chapter VI. 

 Physiology of Animals. 



The Problem of Physiology Ancient Physiology Aristotle Galen 

 Mediaval Physiology Harvey Physiology comes of Age as a Special- 

 ism: Haller Physiology becomes Comparative Advance of Com- 

 parative Physiology Chemical Aspects Physical Aspects Du 

 Bois-Reymond Experimental Physiology The Study of Internal 

 Secretions Analysis of Nervous Mechanism Cellular Physiology 

 The Protoplasmic Movement Pathology Reproduction in Animals. 



The physiologist is pre-eminently an investigator of 

 vital activity. Whether he studies the leaf of a plant or 

 the lung of an animal, a single cell or an The 

 entire organism, his question always is, "How Problem of 

 does this live and work?" He studies struc- Ph y siolo *y- 

 ture too, but only as a means to an end, that he may 

 understand function better. In one of his lectures, 

 Prof. Burdon Sanderson illustrated the physiologist's 

 attitude by the characteristic question, which came to 

 Clerk Maxwell's lips when, as a boy, he was shown 

 some mechanism, " What is the^o of this?", or, if put 

 off by some verbalism, " But what is the particular go 

 of it?" 



Starting with the organism as a whole an intact 

 creature with habits and temperaments, the physio- 

 logists have proceeded, slowly but persistently, to inves- 

 tigate the functions of its organs, the properties of its 

 tissues, and the phases observable in its cells, finally 

 reaching to the full length of the biological tether in the 

 distinctively modern study of protoplasm. It need hardly 

 be said that there is still physiological work being don 



