Vi PREFACE. 



Cullen, in his Nosologia Methodica, T. ii. Prolegom. p. 

 xxix. Similitude quidem morborum in sirnilitudine cau- 

 sse eorum proximse, qualiscunque sit, revera consistit. 

 I have taken the proximate cause for the classic cha- 

 racter. The characters of the orders are taken from 

 the excess, or deficiency, or retrograde action, or other 

 properties, of the proximate cause. The genus is 

 generally derived from the proximate effect. And the 

 species generally from the locality of the disease in the 

 system. 



Many species in this system are termed genera in the 

 systems of other writers; and the species of those wri- 

 ters, are, in consequence, here termed varieties. Thus, 

 in Dr. Cullen's Nosologia, the variola or small-pox is 

 termed a genus, and the distinct and confluent kinds are 

 termed species. But as the infection from the distinct 

 kind frequently produces the confluent kind, and that 

 of the confluent kind frequently produces the distinct; 

 it would seem more analogous to botanical arrange- 

 ment, which these nosologists profess to imitate, to call 

 the distinct and confluent small-pox varieties than spe- 

 cies. Because the species of plants in botanical sys- 

 tems propagate others similar to themselves; which 

 does not uniformly occur in such vegetable productions 

 as are termed varieties. 



In some other genera of nosologists the species have 

 no analogy to each other, either in respect to their 

 proximate cause, or to their proximate effect, though 

 they may be somewhat similar in less essential proper- 

 ties; thus the thin and saline discharge from the nos- 

 trils on going into the cold air of a frosty morning, 

 which is owing to the deficient action of the absorbent 

 vessels ofthenostrils,isone species; and the viscid mucus 

 discharged from the secerning vessels of the same mem- 

 brane, when inflamed, is another species of the same 

 genus, Catarrhus. Which bear no analogy either in 



