864 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



be transmitted by the bite of an insect, as it is not contagious but may 

 be communicated to susceptible horses through blood inoculations. 

 This disease manifests itself by producing severe inflammatory changes 

 in the lungs and in the tissues of the head and neck and is attended 

 by a high mortality. No visible organism has been found which will 

 produce horse sickness and as McFadyean and Nocard have shown that 

 the virus is capable of passing through the finest bacteria-proof filters, 

 this disease is probably caused by an invisible microorganism. Blood 

 containing the microorganisms of horse sickness may be kept in sealed 

 bulbs in the dark at room temperature for more than two years without 

 losing its infectiveness. The virus is quite resistant to drying and 

 may survive heating for ten minutes at a temperature of 75. 



INFANTILE PARALYSIS* 



As indicated by its name, this disease (epidemic poliomyelitis) is 

 usually seen in children. It has long been known to exist in both 

 Europe and America, occurring generally in sporadic form. During 

 the last decade, however, its prevalence has greatly increased and a 

 number of well-defined epidemics have been reported. Though the 

 character of this malady long ago led to the belief that it was caused by 

 a microorganism, this fact was not definitely proven until the year 1909 

 when Landsteiner and Popper in Germany, and Straus and Huntoon 

 and Flexner and Lewis in the United States, succeeded in transmitting 

 the infection to monkeys. So far as is now known, none of the lower 

 animals except monkeys are susceptible. 



The symptoms and effects of infantile paralysis are extremely 

 variable. Paralysis is by no means constant, many cases being vry 

 mild and thus possibly escaping detection. In the severer forms of the 

 disease paralyses of various types and degrees are seen. When recovery 

 takes place the paralysis may appear to improve only to be followed by 

 atrophy of certain groups of muscles, resulting in deformity and per- 

 manent lameness. These effects are caused by the destruction of 

 certain nerve centers in the spinal cord. 



As stated above, the microbial origin of infantile paralysis was first 

 demonstrated by the inoculation of monkeys, Flexner and Lewis having 

 successfully carried the infection through a long series of monkeys by 

 successive intracranial injections of an emulsion of the spinal cord 



* Prepared by M. Dorset. 



