692 



SCIENCE 



[N. S. Vol. XXXVI. No. 934 



about an actively immune state through 

 inoculation with adjusted mixtures of 

 virus and corresponding immune serum. 

 The injection of viruses into animals not 

 themselves subject to infection has, in a 

 few instances, yielded immune sera. In 

 this way a serum for foot and mouth dis- 

 ease has been prepared in the horse. 

 Speaking generally, homologous sera are 

 more active than heterologous, or, in other 

 words, an immune cattle serum will act 

 better in cattle than will immune horse 

 serum; but curative sera in a real sense 

 have not yet been produced for this class 

 of diseases. 



It is of great interest to determine the 

 correspondence between the general data I 

 have just reviewed and the special facts of 

 poliomyelitis which have been shown to 

 arise in consequence of an invasion of the 

 nervous tissue by an ultramicroscopie or 

 filterable virus. We may proceed to check 

 off rapidly the main facts. The virus 

 stands midway in point of size between the 

 finest and coarsest examples. It passes 

 readily through the more coarse and 

 slightly through the finest filters. It is 

 highly resistant to drying, and to light 

 and chemical action. In dust, especially 

 within protein matter, it survives weeks 

 and months; in diffuse daylight indefi- 

 nitely, and resists the action of pure gly- 

 cerine and carbolic acid in 0.5 per cent, 

 solution for many months. When animal 

 tissues containing the virus suffer soften- 

 ing and disintegration or disorganization 

 by mould, the virus survives. Eecovery 

 from poliomyelitis in man and the monkey 

 is attended and produced by an immuniza- 

 tion of the body. During this process 

 microbicidal substances appear in the blood 

 that are capable of neutralizing the active 

 virus. This acquired immunity has, in the 

 monkey, been reinforced by subsequent 



injection of large quantities of the living 

 virus. Active immunity can be achieved 

 by first injecting minute and later large 

 amounts of the virus, and an adjusted 

 mixture of immune serum and active virus 

 will confer a beginning low active im- 

 munity capable of being heightened. Cer- 

 tain alien large animals, among which the 

 horse and sheep are especially worth 

 mentioning, are subject to immunization 

 through injections of emulsions of the 

 spinal cord and brain of paralyzed monk- 

 eys, and can thus be made to yield sera 

 possessing microbicidal power and capable 

 of conferring, as do human and monkey 

 immune sera, a degree of passive im- 

 munity. Thus far no immunizing effect 

 has been accomplished with the dead virus. 

 Unless some growth and multiplication 

 take place no immunity arises. 



These facts show a close correspondence 

 between the properties of the virus of 

 poliomyelitis and those of the ultramicro- 

 scopie organisms in general. There re- 

 main to be considered the data bearing 

 upon the manner of entrance of the polio- 

 myelitic virus into the body or, in other 

 words, upon the mode of infection. Anal- 

 ogy with other diseases produced by filter- 

 able viruses excludes no one of the possible 

 modes, since their manner of entrance is 

 widely varied, as we have seen. This ques- 

 tion is of the utmost importance, since with 

 all diseases prevention is far better than 

 the most perfect cure, and for poliomye- 

 litis there exists at present no specific or 

 true curative treatment. Moreover, for the 

 most part when the disease is first recog- 

 nized it has already caused irreparable 

 damage, and though the more general ex- 

 amination of the spinal fluid obtained by 

 means of lumbar puncture for purposes of 

 diagnosis may possibly lead to a much 

 earlier recognition of the disease, yet its 



