8 Dr. F. W. Mott. Microscopic Changes in the [Feb. 21, 



proliferation. There was also in the subjacent cortical white matter a 

 perivascular glia proliferation. ( Vide figs. 3 and 4, Plate 1, and Photo- 

 micrograph 12.) 



(2) The monkey dying eighteen months after inoculation with Trypano- 

 soma Gambiense, in which the lesion of Sleeping Sickness was found by 

 Major Leishman and described by Captain Harvey.* 



I have found in portions of the brain of this animal (kindly given to me 

 by Major Leishman) a profound neuroglia proliferation, similar to that seen 

 in Dourine and chronic Sleeping Sickness. The lymphocyte proliferation is 

 not very marked, and the cellular proliferation in the perivascular lymphatics 

 is in many parts due more to neuroglial proliferation than lymphocyte 

 infiltration. Photomicrograph 11 and fig. 5, Plate 1, show this proliferation 

 in the sheath of a vessel which has been cut longitudinally. This seems to 

 indicate the pathology of the process, viz., the overgrowth of the perivascular 

 glial tissue meshwork, which stops the proliferated lymphocytes, and leads to 

 their accumulation in the perivascular sheath. 



Conclusions. 



The more chronic the case of trypanosome infection, the more extensive is 

 the glia cell proliferation. The overgrowth of glia tissue is manifested by 

 an increase in number and size of cells and fibrils. Many large cells are 

 seen with branching processes, sending one process to form a foot on the 

 vessel wall, others are seen entering into the formation of a dense reticulum 

 in the perivascular lymphatic space. ( Vide Plate 1, figs. 1 and 5, and 

 Photomicrographs 10, 11, 12.) Normally, the perivascular spaces have 

 only a few delicate septa passing across, which could not in any way impede 

 the flow of the cerebro-spinal fluid and lymphocytes. 



Dr. Eisath, working in my laboratory, has recently shown by a differential 

 method of staining that a large number of the round cellular elements 

 contained in the perivascular infiltration of chronic Sleeping Sickness are not 

 lymphocytes, but the nuclei of neuroglia cells. I have not found this glial 

 proliferation in acute cases of trypanosome disease of animals, only in the 

 chronic case of Dourine, and in the two cases of experimental Sleeping 

 Sickness in monkeys above referred to. The glial proliferation in these cases 

 is in excess of, and appears to precede, the perivascular lymphocyte accumu- 

 lation so constantly found in human Sleeping Sickness, which we now know 

 may be a very chronic disease. Moreover, in most cases of uncomplicated 



* " Report on a Case of Experimental Sleeping Sickness in a Monkey, Macacus 

 rhesus" ' J ournal of the Royal Army Medical Corps,' No. 5, vol. 4. 



