v.] VALUE OF NATURAL HISTORY SCIENCES. 71 



animals there are, he will probably say, beasts, birds, reptiles, 

 fishes, insects, &c. Ask him to define a beast from a reptile, and 

 he cannot do it ; but he says, things like a cow or a horse are 

 beasts, and things like a frog or a lizard are reptiles. You see 

 he does class by type, and not by definition. But how does this 

 classification differ from that of the scientific Zoologist ? How 

 does the meaning of the scientific class-name of &quot; Mammalia &quot; 

 differ from the unscientific of &quot; Beasts &quot; ? 



Why, exactly because the former depends on a definition, the 

 latter on a type. The class Mammalia is scientifically defined as 

 &quot; all animals which have a vertebrated skeleton and suckle their 

 young.&quot; Here is no reference to type, but a definition rigorous 

 enough for a geometrician. And such is the character which 

 every scientific naturalist recognises as that to which his classes 

 must aspire knowing, as he does, that classification by type is 

 simply an acknowledgment of ignorance and a temporary device. 



So much in the way of negative argument as against the 

 reputed differences between Biological and other methods. No 

 such differences, I believe, really exist. The subject-matter of 

 Biological science is different from that of other sciences, but the 

 methods of all are identical ; and these methods are 



1. Observation of facts including under this head that artifi 

 cial observation which is called experiment. 



2. That process of tying up similar facts into bundles, ticketed 

 and ready for use, which is called Comparison and Classification, 

 the results of the process, the ticketed bundles, being named 

 General propositions. 



3. Deduction, which takes us from the general proposition to 

 facts again teaches us, if I may so say, to anticipate from the 

 ticket what is inside the bundle. And finally 



4. Verification, which is the process of ascertaining whether, 

 in point of fact, our anticipation is a correct one. 



Such are the methods of all science whatsoever ; but perhaps 

 you will permit me to give you an illustration of their employ 

 ment in the science of Life ; and I will take as a special case, the 

 establishment of the doctrine of the Circulation of the Blood. 



