SMALLPOX. 321 



poison is apparently excreted by the kidneys, as these organs 

 are frequently and extensively involved, especially in severe 

 cases. 



Class, a few years ago, described a diplococcus which he 

 believed to be the specific cause of scarlet fever. He named 

 it Diplococcus scarlatinas. Proof positive as to its relationship 

 to the disease is wanting, however. Class grew this germ on 

 a mixture of agar-agar and garden earth. It could not be 

 cultivated in any medium which did riot contain earth. 



One attack of scarlet fever confers immunity, although 

 second attacks have been recorded. Scarlatina, like measles, 

 is a disease of youth, arid when it occurs in adults it is as an 

 aggravated form of the disease. 



Smallpox: The exciting cause of smallpox is also unknown. 

 The virus is known to be contained in the pustules, in the 

 desquamating skin, in the sputum, and in the nasal secretions 

 of smallpox patients. The virus retains its virulence for 

 many months. 



Infection is conveyed through the air and by bed -clothing, 

 linen, and other articles that may have been contaminated 

 by the virus ; but the nature of the infection and the method 

 of conveyance have not been determined. The skin and the 

 respiratory tract would naturally suggest themselves as portals 

 of infection, and yet the first symptoms of smallpox, as in 

 measles and scarlatina, are not local but general manifesta- 

 tions indicative of an intoxication. One case of smallpox, 

 unless isolated, may form the nidus of a practically unlimited 

 epidemic. The same is true of scarlet fever. Isolation and 

 protection of the well effectually check the spread of the dis- 

 ease. It is possible that the virus may be inhaled, but, with 

 rare exceptions, smallpox lesions do not develop in the respi- 

 ratory tract. The skin is the usual seat of the exanthematous 

 eruption, and perhaps the infection enters by that channel. 

 Microscopic examination has shown that the tissue-cells in 

 the infected areas contain from one to four spheroidal or 

 slightly irregular bodies which vary in size, the largest being 

 of the size of a cell-nucleus. With nuclear stains they stain 

 more faintly than the nucleus. They are homogeneous. 

 When the hgematoxylin and eosin double stain is used, the 



21 Bact, 



