598 ACUTE INFECTIOUS DISEASES. 



form a ring-shaped swelling at the edge of the pock), we find a mesh- 

 work in the pock pustule, which results from old cells of the rete Mal- 

 pighii, compressed by the exudation, particularly of the central cells 

 of the epithelium dipping down between the papillae. This mesh- 

 work traverses the middle of the pock more particularly, and causes 

 the fan-like formation which has been so much discussed. If the vari- 

 olous inflammation has not extended to the papillae, they are com- 

 pressed and flattened by the pressure of the pock ; in such cases the 

 pock-pustules dry up early. New epidermis forms under the resulting 

 scabs ; when it is fully formed, the scabs fall off. A shallow excava- 

 tion is occasionally left at the point where they have been, as the flat- 

 tening of the papilla is not removed. The case is different when the 

 papilla becomes infiltrated with pus, and breaks down. In such cases 

 the contents of the pustules are changed into a more purulent fluid by 

 the greater admixture of pus-cells, and by the detritus resulting from 

 the breaking down of the papillae. The pustules become more dis- 

 tended, and thus the umbilications (or shallow depressions in the cen- 

 tre) of some pustules are obliterated. Some pocks burst, and allow 

 their contents to trickle out, others dry up ; in the latter case, as the 

 middle part dries first, the umbilication is sometimes renewed. The 

 resulting scabs do not fall off for some time, and they leave depressed, 

 radiated cicatrices, on whose base we may see the dilated openings of 

 the hair-follicles. 



The variety in extent and form of the pocks has induced the divi- 

 sion into different classes. According as the pustules remain separated 

 by intervals of healthy skin, or touch each other, or, lastly, unite to- 

 gether into vesicles, the cases are divided into variolce discretce, cohce- 

 rentes, and confluentes. Where the pocks do not pass beyond the 

 first stage, so that no vesicles form on the sharply-bounded flattened 

 nodules, it is called variola verrucosa. Variola lymphatica or serosa 

 is where the contents of the pock do not become yellow and purulent, 

 but remain a clear or slightly-clouded fluid ; variola cruenta is where 

 I he pocks are colored red or blackish, by the admixture of blood 

 (" black pox "). A form where the contents of the pock are absorbed, 

 and the empty covering alone remains, is called variola siliquosa seu 

 emphysematica ; where the pock is filled with a discolored, ichorous 

 matter, and accompanied by gangrene of the skin, the disease is termed 

 variola gangrenosa. 



We do not find pocks on the serous membranes in autopsy of 

 small-pox patients, but we not unfrequently find the remains of inflam- 

 mation, with haemorrhagic exudation. Sick found fatty, extensive 

 degeneration in the liver, kidneys, heart, and muscles of patients who 

 had died of variola. 



