( xxiii ) 



Development, as distinguished from mere growth, ceases when 

 the pre-ordained form of the organ is completed ; but its arrest may 

 at any period be attended with the growth of the imperfect organ. 

 In this way monsters may be, and are, produced, but no lesion of 

 organogeny in the inferior embryo can elevate the being in the bio- 

 logical scale. A reptile cannot proceed from a fish, a bird from a 

 reptile, a mammal from a bird, and, I may add, a man from an ape. 

 Much has been said as to the powers and effects of natural selection 

 in organisation, but there is a determined line beyond which, higher 

 at least in advancement, it wholly refuses to go. 



It will be thought that, in reference to Biology, the controversy as 

 to the teleological argument and the views of some modern Biologists 

 should be here spoken of. But it seems to me that the observation, 

 investigation, and accumulation of facts is a work more fitting for this 

 Academy than dealing with matters of speculation. "Scientific 

 labour," as I once heard Professor M'Cullagh say, " should have two 

 ends, one subsidiary to the other ; first, the discovery of fact, and the 

 natural sequence of observation ; and next, the correlation of what is 

 thus discovered, with evidences of a .power, immeasurable, inconceiv- 

 able, and all-embracing." 



In relation to the pathological aspects of Biology, the powers of 

 polariscopic analysis have been, in the hands of our late distinguished 

 President, shown to have opened up a new and wide field of investi- 

 gation. In his researches we can see how physical phenomena can 

 touch the mysterious conditions of life. This is not a question of 

 structure, whether it be or be not histological. It is truly one of 

 property, one of the varied results of life on organic form during its 

 appointed period of existence. In diabetes mellitus the renal func- 

 tion, acting under the influence of the nervous power, or, in other 

 words, of animal life, produces results all but identical with those of 

 the living vine or sugar cane. We have here one out of many illus- 

 trations of the views of Serres, that defect or disease in the higher 

 organisms reproduces the normal conditions in those that are inferior ; 

 and this principle we perceive to be true, not alone as to form and 

 structure, but as to the chemical composition of the resulting secretion. 



Of the first of these propositions many examples might be 

 given. The internal ectopia or the existence of the abdominal viscera 

 in the thorax represents the Avant of the diaphragm in birds : 



