CLASS II. 1.3. OF SENSATION. i 81 



ORDO I. 



Increased Sensation. 



GENUS III. 



With the Production of new Vessels by external Membranes or 

 Glands^ with Fever. 



THE diseases of this genus are perhaps all productive of con- 

 tagious matter; or which becomes so by its exposure to the air, 

 either through the cuticle, or by immediate contact with it; 

 such are the matters of the small-pox and measles. The puru- 

 lent matter formed on parts covered from the air by thicker 

 membranes or muscles, as in the preceding genus, does not in- 

 duce fever; and cannot therefore be called contagious; but it 

 acquires this property of producing fever in a few hours, after 

 the abscess has been opened, so as to admit the air to its surface, 

 and may then be said to consist of contagious miasmata. This 

 kind of contagious matter only induces fever, but does not pro- 

 duce other matter with properties similar to its own; and in 

 this respect it differs from the contagious miasmata of small-pox 

 or measles, but resembles those which have their origin in crowd- 

 ed jails; for these produce fever only, which frequently de- 

 stroys the patient; but do not produce other matters similar to 

 themselves; as appears from none of those who died of the jail- 

 fever, caught at the famous black assizes at Oxford, at the be- 

 ginning of this century, having infected their physicians or at- 

 tendants. 



If indeed the matter has continued so long as to become putrid, 

 and thus to have given out air from a part of it, it acquires the 

 power of producing fever; in the same manner as if the ulcer 

 had been opened, and exposed to the common air; instances of 

 which are not unfrequent. And from these circumstances it 

 seems probable, that the matters secreted by the new vessels 

 formed in all kinds of phlegmons, or pustules, are not conta- 

 gious, till they have acquired something from the atmosphere, or 

 from the gas produced by putrefaction; which will account for 

 some phenomena in the lues venerea, cancer, and of other con- 

 tagious secretions on the skin without fever, to be mentioned 

 hereafter. See Class II. 1. 4. 14. 



The theory of contagion has been perplexed by comparing it 

 with fermenting liquors; but the contagious material is shewn 

 in Section XXXIII. to be produced like other secreted matters, 



