ON NOSOLOGY. 453 



but they do not form either genera or species of a disease. Thus, 

 to give an example, a tertian has the general character of an 

 intermittent fever, with the particular circumstance of an 

 interval of forty-eight hours between the beginning of one 

 paroxysm and that of the following. This is a steady and 

 very frequent recurrence ; but we know that besides this, a 

 number of other circumstances frequently accompany it ; par- 

 ticularly a number of intermediate fits of considerable vari- 

 ety. A fit may happen every day, or twice in one day and 

 once in another; but the prevailing character is steady and 

 constant, while the other circumstances of the intermediate fits 

 are more unsteady, constantly shifting and changing, very often 

 in the same patient, and much more frequently in the same 

 epidemic. Hence it is, that in my synopsis I have made a genus 

 of Tertiana, and have marked all the other subdivisions merely 

 as varieties. But here you may be stumbled, as I have given 

 the Tertiana as a genus, and at the same time speak of it as 

 a species ; for, according to the principles of method, that is 

 strictly called a species, which is a concourse of symptoms or 

 a character, not admitting of a subdivision of steady and con- 

 stant particulars. The species therefore is the ultimate char- 

 acter ; and whenever you come to this, it ought, in strict pro- 

 priety, to be called a species. But no system has avoided this 

 difficulty; and it has often been found necessary ts confound 

 genus and species. Thus, in the animal kingdom, Elephas, 

 Noctilio, and many other animals in the other classes, are en- 

 tered into the system of Linnaeus as genera, whereas they 

 are truly species, admitting of no subdivision that is at all 

 steady. The Rhinoceros, also, is a species, although marked 

 as a genus. You will find that in every system, the name 

 of genus and species are in this respect confounded. But 

 the thing to be remarked is, that it is the ultimate concourse, 

 the ultimate character, which you are to have in view ; that 

 this is the character in Nosology no matter whether you call 

 it species or genus which is the fixed object of our practice, 

 and the chief object ; for, though I know that the study of the 

 variety may be necessary, it is by no means universally so. And 

 I would here observe, that, though I say we can only aim at a gen- 

 eric practice, I now say more clearly, that such genera may be 





