282 PALAEONTOLOGY. 



1762, of Lyonnet, are unsurpassed examples of this monographical 

 species of anatomical science. 



But the anatomist may apply himself to a particular organ instead of 

 a particular species ; and may trace the modifications of such organ as 

 far it can be determined to exist in the animal kingdom : in which 

 quest, if begun, as anatomy is usually entered upon, by the human 

 subject, he would, with most organs, find them gradually losing some 

 feature of essential complexity, and becoming reduced to a more and 

 more simple condition. 



This kind or way of anatomy occupied a great proportion of John 

 Hunter's time. He thus, so far as opportunities presented themselves, 

 or could be availed of, followed out organ after organ, until he had 

 embraced the whole scheme of organs in the most complicated organism ; 

 and, having so traced down the simphfying modifications presented 

 by the animals as they progressively departed from the perfection of 

 the human type, he then assembled the evidences of his labours, re- 

 versed the order in which they had been investigated, and beginning 

 with the simplest form which he had detected of each given organ, 

 placed after it, in succession, the progressively more complex forms of 

 the same organ, the series culminating, in most cases, with that which 

 exists in the human body. Having thus laboriously obtained his 

 knowledge and his material evidences of the modifications of particular 

 organs analytically, Hunter strove to impart the higher conclusions 

 deducible from those evidences by presenting them in the synthetical 

 order requisite for such generalizations ; as in the arrangement which 

 governs the disposition of the Physiological Collection in the Museum. 



A third kind of anatomy necessarily follows the synthetical route : it 

 is that which takes the embryo of a particular species for its subject ; 

 and, starting from the moment of impregnation, or, perhaps, with a 

 preliminary research into the progressive formation of the impregnating 

 principle and its nidus, or material for operation — the development, 

 viz., of the spermatozoid and the ovum — then proceeds to follow out 

 the consequences of their mysterious union and mutual reaction. In 

 this way each organ is traced step by step in its evolution, until it 

 attains the condition suitable for the life-work of the adult parents of 

 the embryo under investigation. And when the subject selected for 

 the inquiry happens to have belonged to one of the higher classes of 

 animals, it has been found that the gradational series of changes which 

 a given organ presents in the course of its development, resemble in 

 some degree the chief steps or links in the series of mature organs 

 derived from different species according to the second mode of inquiry. 



A fourth way of anatomy is that which, beginning with an investigation 



