NEUROTOXINS OF SNAKE VENOM 151 



employed were those contained in the preoesophageal ganglia. The ganglia 

 having been excised from the living animal, they were carefully and minutely 

 teased in sea water, and then brought under the influence of venom also 

 dissolved in sea water. Observations were made under the microscope at inter- 

 vals up to 24 hours. Control preparations of the cells suspended in sea water, 

 were examined at corresponding intervals. The temperature was that of the 

 room during the summer months. A brief summary of facts follows. 



CELLS OF SYCOTYPUS. 

 (Plates 23, 24, 25.) 



The controls show two kinds of nerve cells: (a) pigmented and (b) non- 

 pigmented. Between the cells and originating from them numerous fine, 

 non-medullated fibrils occur. The cells are large, reaching 40 /*, and are 

 readily observed in unstained preparations. They are oval or elliptical in 

 form, and granular. The pigmented cells contain many highly refractive 

 yellow granules of varying size, which more or less completely obscure the 

 nuclei. The pigment is abundant and granular; there is no diffuse pigment. 

 The non-pigmented cells may equal the first in size and also in number of 

 granules. These granules are markedly uniform in size, round in form, and 

 give a dark grayish hue to the protoplasma, in which they occur in such quan- 

 tity as to obscure the nuclei. The unpigmented cells are far less numerous 

 than the previous ones. While the first exist in groups, the second tend to 

 appear singly or in small clumps only. The two kinds of cells show marked 

 differences of resistance to venom in solution. 



In simple sea water, if protected from evaporation, the nerve cells undergo 

 no appreciable change within 24 hours. After that the cells suffer changes in 

 distinctness of outline, but show no evidence of disintegration for some time. 



One per cent cobra venom : Five minutes : The cells are swollen and rendered 

 less distinctly visible. Twenty minutes: Swelling increased; nerve fiber 

 coarsely granular; yellow pigment granules beginning to undergo solution. 

 Sixty minutes: Protoplasma of large pigmented cells very indistinct; pig- 

 mented cells disappearing. Twenty-four hours: Almost complete dissolu- 

 tion of the tissue. Here and there some of the large yellow pigment granules 

 have coalesced into globules averaging in size the nucleus of a cell. 



One per cent water-moccasin venom: This venom is distinguished in effect 

 from cobra only by its somewhat weaker and slower action. At the end of 

 24 hours the cell bodies have been dissolved and the pigment liberated, but 

 the latter may still retain the general form of the cell from which it came. 

 Occasionally the granules may be seen to have coalesced, as in the case of 

 cobra-venom solution. The nerve fibers, which are even more resistant to 

 cobra venom than the cell protoplasma, finally vanish entirely. 



One per cent crotalus venom : This venom is much weaker in action than the 

 other two. Even after contact for 24 hours many of the cells still keep their 

 outlines, and the pigment and many fibrils are still preserved and easily visible. 



