November 22, 1912] 



SCIENCE 



695 



nodes whieh thus form a notable exception 

 to the general internal organs of the body. 



"We have now followed the route by 

 which the poliomyelitic virus, implanted 

 within the apparently closed cavity of the 

 skull, reaches the exterior of the body. It 

 is obvious that in the spontaneous form of 

 the infection in man no such mode of 

 introduction of the virus can occur. The 

 virus must indeed enter the human body 

 by some external channel, after which it 

 seeks and becomes implanted upon the cen- 

 tral nervous system. It is known that in 

 monkeys the virus is incapable of passing 

 the barrier of the unbroken or slightly 

 abraded skin, of being taken up from the 

 stomach or intestine unless the functions 

 of these organs are previously disturbed 

 and arrested by opium, and it is further 

 known that it traverses with difficulty or 

 even not at all the substance of the lungs. 

 On the other hand, it is established that 

 the virus passes with readiness and con- 

 stancy from the intact or practically intact 

 mucous membrane of the nose to the cen- 

 tral nervous system. 



To illustrate this point I wish to describe 

 briefly an experiment. The spinal cord of 

 a paralyzed monkey always contains the 

 virus we are considering. If a camel's 

 hair pencil or pledget of cotton is covered 

 with some of the broken up tissue of such 

 a cord and painted upon the mucous mem- 

 brane of rhesus monkeys, these animals 

 will develop in due time the paralysis and 

 other symptoms of poliomyelitis. Hence 

 the virus enters the body from this surface 

 even though no gross injury has been in- 

 flicted upon the membrane. We shotild 

 now ask ourselves if the virus actually as- 

 cends to the brain by the direct path of 

 the olfactory nerves or indirectly after 

 first entering the blood. This is the same 

 question that has been buffeted about in 



regard to epidemic meningitis. The men- 

 ingococcus is found in the nasal mucous 

 membrane of persons in contact with cases 

 of meningitis, and in the sick themselves. 

 It is not disputed that the meningococci 

 settle on this membrane, but opinion is 

 divided as to whether it goes at once to 

 the membranes of the brain or first pene- 

 trates into the blood. To produce menin- 

 gitis in monkeys it does not suffice to in- 

 oculate the nasal membrane; the menin- 

 gococci must be injected into the mem- 

 branes themselves. But so inoculated they 

 escape in part along the nerves of smell 

 into the nose. The virus of poliomyelitis 

 is so active that implantation in the nose 

 does suffice to cause infection. If a monkey 

 is sacrificed about forty-eight hours after 

 an intranasal inoculation, and the brain 

 and spinal cord are removed and then the 

 olfactory lobes and portions of the medulla 

 and spinal cord are separately inoculated 

 into other monkeys, infection is produced 

 by the olfactory lobes alone, since in this 

 brief period the virus has not yet reached 

 other and more distant parts of the ner- 

 vous organs. Were the virus distributed 

 by the blood, the medulla and spinal cord 

 would have become infective, rather than 

 the olfactory lobes, since they exhibit a 

 greater selective affinity for the parasite. 

 The conclusion, therefore, is unavoidable 

 that the virus ascends by the nerves of 

 smell to the brain, multiplies first in and 

 about the olfactory lobes and, in time, 

 passes, as I believe, into the cerebrospinal 

 liquid which carries it to all parts of the 

 nervous organs. We have already learned 

 that the virus can pass along a large nerve, 

 such as the sciatic, which carries it first to 

 the lumbar cord, whence it ascends to 

 higher levels; we need not, therefore, be 

 astonished to find that it can wander along 

 the olfactory nerves and then descend to 



