128 PROTOPLASM 



ture of the nuclei of these cells I was also able to make out 

 some facts as to the structural relations of their protoplasm. 

 Since, in the investigation of these nuclei, I was making use 

 of hsematoxylin to obtain the differential stain described by 

 me on a former occasion (1890), which can only be dis- 

 tinctly shown in material preserved in alcohol, the observa- 

 tions to be described were undertaken upon blood corpuscles 

 which were preserved in iodine-alcohol of 40 per cent, then 

 stained in acid haematoxylin, and mounted in Damar. As 

 in a large number of blood corpuscles prepared in this manner, 

 the external form proved to be faultlessly preserved, and as 

 from many experiments carried on directly under the cover- 

 slip with iodine alcohol, it was known that this reagent gives 

 good preservation of the finest structural details of the pro- 

 toplasm, I have not the slightest fear that the somewhat 

 unusual method of preservation produced abnormal altera- 

 tions in the blood corpuscles. 



On careful examination of a large number of well-pre- 

 served blood cells it may be recognised at the outset that they 

 are enveloped at their surface by a pellicle-like membrane 

 fairly thick and even distinctly double contoured (Plate X. 

 Fig. 1, p\ beneath which runs a clear border distinctly 

 radially striated (alv). This border can be followed quite 

 easily both in the surface view of the blood corpuscle (Fig. 

 1, a) and in optical median longitudinal section (Fig. 

 1, V). In the latter view particularly it may frequently be 

 seen very beautifully. The pellicle-like envelope together 

 with the radially striated border, represent, without doubt, 

 an external layer of alveoli of similar structure to that 

 which we described above in living Vorticellse, for example. 

 Beneath the marginal alveolar layer there can be seen in 

 surface view a girdle-like zone of finely -meshed internal 

 protoplasm, which, however, only attains from about J to J 

 the width of the transverse radius of the corpuscle (g). 

 This zone becomes still plainer in the optical median sec- 

 tion, when it is seen that the internal protoplasm only 

 forms a marginal ring or ridge (g), which passes down 

 on to the flat surfaces of the corpuscle ; but here it very soon 

 thins out, so that the flattened sides throughout the greater 



