194 



Prof. E. A. Schaf< r 



[Feb. IL>, 



with the appliances necessary for photographing by the electric light, 

 I was unable to obtain instantaneous photographs, and could not 

 photograph the corpuscles while actually living and moving. I 

 accordingly adopted a method of suddenly killing the corpuscles 

 whilst still in the amoeboid condition with their pseudopodia extended. 

 It is well known that with most methods which are employed to fix 

 the white blood corpuscles there is time for a contraction of the 

 protoplasm to be produced, so that the pseudopodia are withdrawn 

 and the corpuscle becomes spherical. The method which I have used 

 consists in the instantaneous application of a jet of steam to the 

 surface of the cover-glass. A preparation of blood, preferably from 

 the newt (Triton cristatus), is made either in a moist chamber or in 

 the usnal way on a glass slide. In a short time the white corpuscles 

 become highly amoeboid and throw out psendopodia, which may- 

 spread themselves in a thin layer upon the cover glass in a manner 

 which is perfectly adapted for their being accurately observed. If 

 the steam be now turned on for an instant, the cells are suddenly 

 killed, and remain exactly in the condition in which they happened to 

 be when the heat was applied. They can be examined and phot 

 graphed thus, or may first be stained by luematoxylin, with or with- 

 out being previously treated with alcohol. In all cases they exhibit 

 the same general structural appearances, and these appearances can 

 even be detected, but with greater difficulty, in the cell whilst still 

 living. 



Leaving the nucleus, which beautifully exhibits the karyoplasmic 

 network, out of consideration, the most striking point in all amoeboid 

 white corpuscles thus prepared is the contrast between the proto- 

 plasm of the body of the cell and that of the pseudopodia. For 

 whilst the former exhibits, according to focus, either a finely 

 punctated or a reticular aspect, and stains decidedly with hiemato- 

 xylin, the pseudopodia exhibit not the faintest trace of structt 

 and re-main almost entirely unstained. 



In other words, the protoplasm is composed of two morphologically 

 distinct parts, one which exhibits a reticnlar arrangement and has an 

 affinity for hsematoxylin, and another which shows to the best optical 

 appliances no structural arrangement, and is also chemically different, 

 as is shown by its behaviour to staining reagents. 



The observation here recorded is not an isolated one. Almost all 

 observers who have given special attention to the matter have failed 

 to detect a reticular structure in pseudopodia, whether of 

 amoeboid cells of higher organisms or of the Bhizopoda. To Butschli's 

 theory of the structure and activity of protoplasm,* whereby he 

 endeavours to show that the reticular appearance and amoeboid 

 phenomena may be explained on the assumption that protoplasm is 

 ' Heidelberg Verhandlungen,' 1890 ; and ' Biologisches Centralblatt,' 1890. 



