382 Acute Anterior Poliomyelitis 



when the attention was attracted, and a wrinkled and mobile rather 

 than smooth and placid face. The onset of the disease is sudden, 

 with or without the given signs, and consists of paralysis. In gen- 

 eral, any of the larger voluntary muscle groups may be affected; 

 other groups may be weak or partially paralyzed. The paralysis 

 may be of all grades of completeness. There may be some anes- 

 thesia; occasionally there was evidence of pain. The animals may 

 die or they may recover. In the latter case the paralysis some- 

 times entirely disappears; more frequently it persists and the para- 

 lyzed member gradually stiffens and is deformed by contractures. 



In the dead monkeys, or those that were killed for study, the 

 chief lesions were in the gray matter of the central nervous sys- 

 tem and consisted of edema, diffuse livid injections of the blood- 

 vessels and punctiform and pin-head-sized hemorrhages. When 

 healing sets in, the lesions are firmer, paler, non-circumscribed, and 

 raised somewhat above the level of the surrounding gray and white 

 matter. 



The chief histological changes were also in the gray matter es- 

 pecially in the cord, where they occurred in either the anterior or 

 posterior horns, but more frequently and more extensively in the 

 anterior horns. There was a high degree of cellular infiltration of 

 the perivascular spaces, edema of the spaces, and hemorrhage into 

 the spaces. From the spaces the cells often passed into the ground 

 substance. But independent foci of small cells, edema and hemor- 

 rhage also existed in the nervous tissue. The nerve cells often 

 showed degeneration which consisted of hyaline transformation 

 and necrosis leading to loss of the tigroid substance, cell-processes, 

 nuclei, etc. Often the cell was surrounded by lymphocytes or in- 

 vaded by polymorphonuclear leukocytes. Sometimes the nerve- 

 cells had disappeared and the leukocytes taken their places. Ulti- 

 mately, a part of the nervous elements would be removed and re- 

 placed by an indefinite cellular tissue, containing many compound 

 granular corpuscles. 



The monkeys were infected by various methods, the first being 

 the direct inoculation of the brain by a needle introduced through 

 the opening made by a small trephine. They found, however, 

 that the virus readily finds its way to the nervous system when 

 introduced subcutaneously, and less readily when introduced 

 intraperitoneally. The blood of the infected animal contains the 

 virus at the beginning of the attack but how richly was not deter- 

 mined. The crebro-spinal fluid also contains it at the time the 

 palsy appears. The vaso-pharyngeal mucosa also contains it, and 

 can convey it to other animals. 



The virus readily passed through Berkefeld filters, and the clear 

 filtrate thus obtained, when injected into monkeys by the intra- 

 cerebral or subcut'aneous routes, regularly produced the disease 

 in an infectious form so that it was clear that the lesions were in- 



