PKRIOD OF INCUBATION. 71 



fever rarely abates, and its continuance leads to its 

 assuming a typhoid condition. The mucous mem- 

 branes, both of the respiratory and digestive organs, 

 participate in the morbid state of the skin, and the 

 inflammation has a great tendency to end in sphacelus. 

 A viscid mucous secretion adheres to the nasal open- 

 ings, plugs them up, and often produces suffocation. 

 Purulent formations take place in the subcutaneous 

 cellular tissue, and uncontrollable diarrhoea is fre- 

 quently associated with confluent variola. These are so 

 many additional causes for its increased malignancy. 



Many affections which attack both man and animals 

 possess the singular property of remaining latent for a 

 greater or shorter time after their respective poisons 

 have been received into the system ; hydrophobia, 

 glanders, farcy, the small-pox, and several others, 

 belong to this class. This pe?'lod of bicuhation is found 

 to vary in different diseases, and also in the same 

 disease at different times: it is influenced by many 

 external circumstances, as well as by the peculiar state 

 of the patient's constitution, — such as the mode in 

 which the poison is received, the heat of the weather, 

 temperament of the animal, freedom from other com- 

 plaints, &c. None of these causes can be said to 

 prevent, although some of them will retard and others 

 facilitate, the breaking out of the eniption. 



Both in natural and inoculated small-pox the tem- 

 perature has much to do with the early appearance of 

 the constitutional symptoms, which declare themselves 

 sooner in summer than in winter. Hurtrel d'Arboval 

 remarks, that the malady will often shew itself in ten 

 or twelve davs in warm weather, but will remain dor- 

 mant for double that time when the temperature is 



