SECT. III.] PROPERTIES OF THE VIS NERVOSA. 403 



rant of the nature of the vis nervosa in general, much more may 

 this peculiar vis nervosa be unknown to us, the visible eflPects 

 of which can only be observed. If any person would collect 

 these from his personal observation and from medical writings, 

 and arrange them well, he would certainly accomplish a useful 

 work, from which we might hope to obtain much light for 

 understanding the functions of the nervous system, and much 

 for the cm^e of its diseases. And Haller spoke truly of idio- 

 syncrasy, when he said : " As yet this field has certainly not 

 been sufficiently cultivated, and there is the prospect of an 

 abundant harvest from it.^^ ^ As in this dissertation I propose 

 only to give an introduction to the functions of the nervous 

 system, rather than to work out a complete treatise, I shall 

 only enumerate a few examples of idiosyncrasy, hoping from 

 others a full systematic account. 



It happens to some men, in other respects perfectly healthy, 

 that they cannot see, taste, or even hear certain things, but they 

 are affected unpleasantly, and sometimes to fainting. Some 

 cannot be present at a venesection, and see the blood flow, with- 

 out fainting away. I know a female who, when young, could 

 never see the beet-root that is usually placed on the table, without 

 swooning and fainting; she was at last by habit enabled to look at 

 it, but could never eat it. The exhalations of a cat, although 

 concealed, excite in some men disquietude, perspiration, and 

 fainting ; an example of this kind is narrated by Kaaw;^ and also 

 the history of a man who was always affected with a bleeding 

 at the nose, from the odour of cheese. Fainting, in some, is 

 induced by the fragrance of roses ; and the pale rose of a 

 pleasant odour, the red, unpleasant. "* Fainting has also been 

 excited by the odour of apples.^ Strawberries have produced 

 remarkable symptoms.^ Musk and civet can excite in some 

 persons violent hysterical attacks, which in others are induced 

 by the fetid gums. We may meet every day with illustrations 

 of idiosyncrasy of taste, for we see some persons esteem articles 

 of diet as delicacies which others abhor : I myself, when young, 

 had such an aversion for spinach, beet-root, and cod-fish, that 



• Elena. Phys., torn, iv, p. 575. 



2 Impet. Faciens dictum Hippocrati, § 408, p. 358. 

 ^ Eph. Nat. Cur., Dec. ii, An. v, observ. 8. 



* Ibid,, An. I, observ., 72. 

 Ibid., An. v, observ., 214. 



