November 22, 1912] 



SCIENCE 



693 



prevention will always remain the result 

 to be aimed at. It is quite certain that an 

 understanding of the mode of infection 

 would lead inevitably to the framing of 

 measures of prevention that with reason- 

 able certainty could be expected to exer- 

 cise control over the epidemic spread. 



Two answers may be returned to the 

 question: one based upon observation of 

 human cases of poliomyelitis, and the 

 other based upon experimental tests ar- 

 ranged to elicit specific replies. The first 

 answer can not achieve anything higher 

 than strong probability; the second, to be 

 valid, must explain the phenomena attend- 

 ing the human infection as well as those of 

 the experimental disease. We are asked 

 to account for certain data, of which the 

 following is a brief statement. Epidemic 

 poliomyelitis is preeminently a disease of 

 early childhood and finds the highest per- 

 centage of its victims in the first five years 

 of life, but does not wholly spare older 

 children or even adults. It is admittedly 

 infectious; and while it is true that many 

 more instances of single than of multiple 

 cases occur, yet multiple ones are not by 

 any means rare. The prevailing views on 

 this topic are being modified rapidly by 

 the recognition of the abortive and am- 

 bulant examples of the disease. The pe- 

 riod of greatest prevalence is during the 

 months of August, September and October 

 in the northern hemisphere, and the corre- 

 sponding months in the southern hemi- 

 sphere, but the epidemic begins in the early 

 spring and summer months and the disease 

 does not wholly disappear during the win- 

 ter months. It does not, therefore, neces- 

 sarily die out at any period of the year. 

 In endeavoring to trace the avenue of 

 entrance of the virus into the body certain 

 facts regarding its distribution in the body 

 should be recapitulated and considered. 



The infectious agent of poliomyelitis at- 

 tacks chiefly the central nervous system. 

 Indeed, it has been detected regularly in 

 the spinal cord and brain and in the mes- 

 enteric lymph nodes among all the internal 

 organs. It has also been detected in the 

 mucous membrane of the nose and throat, 

 and in the mucus secretions of this mem- 

 brane, and in the mucus secretions of the 

 stomach, and the small and large intestine. 

 The virus has not been detected in such im- 

 portant organs as the spleen, kidneys, liver 

 or bone marrow. The fact is significant, 

 but in attempting to interpret it, account 

 should be taken of the circumstance that 

 at present we possess one means only of 

 detecting the virus, and that is its trans- 

 mission to monkeys, in which it produces 

 characteristic paralyses and anatomical 

 changes. On this account small quantities 

 of the virus may conceivably escape dis- 

 covery. However, the conclusion is none 

 the less inevitable that detectable amounts 

 of the poliomyelitic virus exist only in the 

 few situations and organs mentioned. The 

 distribution of the virus is identical in 

 human beings, the subjects of the so-called 

 spontaneous poliomyelitis, and in monkeys, 

 in which the experimental affection is pro- 

 duced. Nor does it matter how the experi- 

 mental inoculation is accomplished and 

 whether the virus is introduced by injec- 

 tion into the brain or large nerves or sub- 

 cutaneous tissue or peritoneum, or whether 

 it is merely applied to the nasal mucous 

 membrane, which, it should be emphasized, 

 next to direct intracerebral injection, af- 

 fords the surest means of causing the ex- 

 perimental disease. In whatever way the 

 infection is produced purposely, the dis- 

 tribution of the virus in infected monkeys 

 is the same as in infected human beings. 



The virus is one that is not known to 

 increase aside from the infected body, and 



