658 DISEASES CAUSED BY FILTRABLE VIRUS 



the cells of corneal lesions experimentally produced in rabbits. Guar- 

 nieri claimed that he distinguished both cytoplasm and nucleus in these 

 bodies and described both binary division and reproduction by sporu- 

 lation as in the sporozoa. He named the supposed protozoan "Cy- 

 toryctes variolas." At about the same time Monti l described similar 

 bodies in the cells of the Malpighian layer of the skin covering smallpox 

 lesions and, a few years later, Clarke 2 confirmed the researches of 

 Guarnieri. Subsequently, many researches were carried out on the 

 same subject in this country, the most notable being those of Council- 

 man, 3 Magrath and Brinckerhoff, and of Calkins. 4 The former authors 

 came to the distinct conclusion that the bodies seen by Guarnieri were 

 parasites, and the latter author even described a distinct life-eye 1 ^ 

 for these parasites comparable to that of some protozoa. 



These researches, however, are by no means absolutely convincing, 

 and Ewing, 5 while admitting that the vaccine bodies are probably 

 specific for variola, calls attention to the fact that specific cell-degen- 

 erations or inclusions are found in diphtheria, measles, glanders, rabies, 

 and other infectious processes, which can not be regarded as in any 

 way related to these diseases etiologically, and suggests the probability 

 of a similar interpretation for the vaccine bodies. Much has been said 

 on both sides of the question since that time, and the problem can not 

 be regarded as settled. The burden of proof, of course, rests upon 

 those who claim the discovery of a specific microorganism, and absolute 

 proof will probably be lacking until our experimental methods are such 

 as will permit of other than purely morphological demonstration. 



Whatever the actual causative agent may be, it is certain that the 

 disease is transmitted with extreme ease actual contact, direct or in- 

 direct, with a patient being unnecessaiy for its transmission. For this 

 reason the disease is often spoken of as being "air borne." While we 

 have no certain knowledge of the portal of entry through which the virus 

 invades the human body, many considerations have made it seem plausible 

 that this may take place through the mucosa of the upper respiratory tract. 



Our knowledge of the means of defense against the malady is for- 

 tunately more advanced than is that of its etiology. It has been known 

 for centuries that one attack of smallpox protects against subsequent 

 attacks. This knowledge was made use of by the physicians of ancient 

 China and India, who, during mild epidemics, exposed healthy children 



1 Monti, Cent, f . Bakt., I, xvi. 2 Clarke, Brit. Med. Jour., 2, 1894. 



3 Councilman, Magrath, and Brinckerhoff, Jour. Med. Res., xi, 1904. 



4 Calkins, Jour. Med. Res., xi, 1904. 6 Ewing, Jour. Med. Res., xiii, 1905. 



