94 SCIENCE IN IHE LAST HALF CENTURY. 



the labors of the philosophical taxouoniist must keep iu view. But it 

 is au eud which can uot be attained until the progress of palaeontology 

 has given us far more insight than we yet possess into the historical 

 facts of the case. Much of the speculative " phylogeny," which abounds 

 among my present contemporaries, reminds me very forcibly of the 

 speculative morphology, unchecked by a knowledge of development, 

 which was rife iu my youth. As hypothesis, suggesting inquiry iu this 

 or that direction, it is often extremely useful ; but when the product 

 of such speculation is placed on a level with those generalizations of 

 mor[)hological truths which are reinesented by the definitions of natural 

 groups, it tends to confuse fancy with fact and to create mere disorder. 

 We are in danger of drifting into a new " I^atur-Philosophie " worse 

 than the old, because there is less excuse for it. Boyle did great serv- 

 ice to science by his "Sceptical Chemist," and I am incliued to think 

 that at the present day a " Sceptical Biologist" might exert an equally 

 beneficent influence. 



PHYSIOLOGY. 



Whoso wishes to gain a clear conception of the progress of physiology 

 since 1837, will do well to compare Miillei's " Physiology," which ap- 

 ])eared in 1S35, and Drapiez's edition of liichard's " Nouveaux Elemeuts 

 de Botauique," published in 1837, with any of the present hand-books 

 of animal and vegetable physiology. Miiller's work was a masterpiece, 

 unsurpassed since the time of Haller, and Kichard's book enjoyed a 

 great reputation at the time ; but their successors transport one into a 

 new world. That which characterizes the new physiology, is that it is 

 permeated by, and indeed based upon conceptions which, though uot 

 wholly absent, are but dawning on the minds of the older writers. 



Modern physiology sets forth as its chief ends : Firstly, the ascertain- 

 ment of the facts and conditions of cell-life in general. Secondly, in 

 composite organisms, the analysis of the functions of organs into those 

 of the cells of which they are composed. Thirdl}^ the explication of 

 the processes by which this local cell-life is directly or indirectly con- 

 trolled and brought into relation with the life of the rest of the cells 

 which compose the organism. Fourthly, the investigation of the phe- 

 nomena of life iu general, ou the assum])tion that the physical and chem- 

 ical processes which take place in the living body are of the same order 

 as those which take place out of it ; and that whatever energy is exerted 

 in producing such phenomena is derived from the commou stock of en- 

 ergy in the universe. In the fifth place modern physiology investigates 

 the relation between physical and psychical phenomena, on the assum])- 

 tion that molecular changes indefinite portions of nervous matter stand 

 in the relation of necessary antecedents to definite mental states and 

 operations. The work which has been done in each of the directions 

 here indicated is vast, and the accumulation of solid knowledge, which 

 has been effected, is correspoudiugly great. For the first time in the 



