670 DR JAMES W. DAWSON ON 



in the spinal cord was produced in both instances by injected lymph which spread 

 by the same path — along the adventitial lymph spaces of the vessels entering from 

 the pia, and therefore attacked the same cells, those of the adventitial sheath of 

 the vessels. The plasma cell is looked upon as the type of cell characteristic of 

 subacute inflammation, and the polyblast as characteristic of an acute inflammation 

 in the central nervous system. If the toxin or organism gaining entrance to the 

 central nervous system by this source be weak, or penetrate the tissues slowly, no 

 other phenomena but that of adventitial proliferation need occur for some time, and 

 the changes in the cord diminish in degree from without inwards. 



These experiments tend to prove that infection passing into the cord by the 

 lymphatic system takes a definite course, that the structures of the cord and the 

 nerves react to infection by this path in a definite manner, and that the inflamma- 

 tion can be propagated by the toxic lymph to parts distant from the focus of 

 greatest intensity. It is recognised that when once the inflammatory condition 

 has been established within the spinal cord, the toxic lymph spreads by direct 

 continuity, and this continuity of extension is looked upon as characteristic of 

 lymphogenous infections. Numerous clinical data, from cases in which peripheral 

 inflammatory foci existed, have been brought forward by Orr and Rows, in support 

 of their experimental work, to demonstrate the facility with which infection spreads 

 along the lymph sheaths of nerves to the spinal cord. Here also the histological 

 changes in the membranes and nervous tissues showed that the reaction varies with 

 the potency of the irritant, and that the degree of reaction in the nervous tissues 

 diminishes from without inwards. In connection with these changes the cord 

 infection which sometimes follows inflammation of the urinary bladder is referred 

 to and is of interest in relation to the evidences of inflammatory changes in the 

 membranes and in the peripheral vessels of the cord found in some of our cases. 

 Orr and Rows further apply this principle of lymphogenous infection to acute 

 polio-myelitis and general paralysis. They look upon the histological changes in 

 the former disease as showing no essential differences to those found in their acute 

 cases — in both the preponderating cell type is the polyblast. The changes in 

 general paralysis also appear explicable only by the presence of toxins of organisms 

 gaining access to the lymph which bathes the brain and membranes and circulates 

 in the adventitial lymph spaces of the cortical vessels, calling forth a chronic peri- 

 arteritis of a plasma-cell type. 



In relation to acute polio-myelitis it may be stated that experimental evidence 

 proves without doubt that it can be produced by lymphogenous infection, and the 

 view that the virus may enter by means of the lymphatics and thus exert its first 

 effect upon the meninges is strengthened by the anatomical findings (Peabody, 

 Draper, and Dochez). The earliest change described in the nervous system is 

 hypersemia and the collection of numbers of small mono-nucleated cells in the peri- 

 vascular lymph spaces of the blood-vessels of the lepto-meninges. The lymph spaces 



