1 8 MEMORIAL SKETCH. 



facts of chemistry, comparative anatomy, and physiology, 

 he dwelt at length on the analogy between the forms of 

 the respiratory apparatus in the two great classes ; he 

 showed that it held good with regard to their functions 

 also, and he even extended it to digestion. Nor did he fail 

 to point out the simplicity and uniformity of the processes 

 into which these apparently complicated phenomena might 

 be resolved, and the similarity of the means by which they 

 were carried into effect. 



The theme thus started continued to occupy his mind 

 while he was pursuing his professional studies at Edinburgh, 

 in the University and the Infirmary, under Professors Alison 

 and Christison. Immediately after his arrival, he had re- 

 ported to his sisters, in November, 1835, the actual com- 

 mencement of his cherished project. 



I have begun to work at my book, and have nearly finished 

 the organs of support, in which I shall bring forward a number 

 of most beautiful analogies which Roget has omitted from 

 his evident ignorance of Vegetable Physiology. I shall read it 

 soon as a paper at the Royal Medical Society, of which I am 

 a member. I think these debates will be of great service to me, 

 as they evidently are of a very high character. 



This central idea, accordingly, runs through the essays 

 of the next few years, which contain the germs of various 

 biological principles destined to receive clearer enuncia- 

 tion afterwards from himself and others. In the summer 

 of 1836, he is already in communication with Dr. (sub- 

 sequently Sir John) Forbes, who had enrolled him among 

 the contributors to the recently established British and 

 Foreign Medical Reviezv. Dr. Forbes had entrusted to him 

 a number of new books on vegetable physiology ; but the 

 reviewer told his father (July 4, 1836) that his essay would 

 be "principally devoted to pointing out the analogies 

 "between animals and vegetables, and the advantages of 



