1891. J On the Structure of Amoeboid Protoplasm, 8fc. 195 



not an actual network with enchylema, bnt rather a frothy mixture 

 of two dissimilar substances, this absence of all apparent structure in 

 pseudopodia offers an admittedly serious difficulty, which he en- 

 leavours to surmount by assuming that the same frothy structure is 

 sally present in the pseudopodia as in the body of the cell, but that 

 owing to thinning out it cannot be detected. But apart from the 

 unlikelihood of our not noticing such structure in the pseudopodia if 

 it were really present, since they are especially well adapted for 

 minute observation, the reticular and the homogeneous substances 

 should, according to this assumption, pass gradually the one into the 

 other, for the thinning-off of the pseudopodia is frequently gradual. 

 The contrary is, however, the case. The line of demarcation of the 

 reticular substance is always quite sharp, and does not thin off into 

 the homogeneous substance of the pseudopodia. 



Strieker's photograph is also really evidence in the same direction. 

 The corpuscle taken is spherical or nearly so, i.e., is in the contracted 

 andition. It has, however, one small pseudopodium. This is abso- 

 itely without structure ; it is the spherical part of the cell which 

 lows the reticulum. 



It is well known that if white corpuscles (and contracted amoeboid 

 ?ells generally) are artificially stimulated, they are always spherical. 

 The spherical form is, in fact, the contracted condition ; it is only in 

 the absence of any obvious source of excitation that the corpuscle 

 >ws out pseudopodia. The spherical condition is immediately 

 produced by electrical or mechanical stimuli ; no doubt, the constant 

 icchanical stimulation which the cells receive in the circulating 

 lood maintains them in the spherical form which they always 

 diibit whilst moving within the blood-vessels. Possibly, also, the 

 Dntact of a foreign particle, causing the contraction and with- 

 Irawal of the protoplasm which it touches, and the consequent 

 iception of the particle, is another instance of mechanical stimula- 

 tion. 



Now, in the contracted corpuscle, the whole cell appears reticular, 

 id the reticulation is even better marked, i.e., coarser, than that 

 sen in the spread out corpuscle. The pseudopodial protoplasm or 

 iyaloplasm has, in fact, been withdrawn into the meshes of the 

 imework or spongioplasm. 



The protoplasm of such an amoeboid cell as the white blood 

 rrpuscle may, therefore, be regarded as composed of two distinct 

 ibstances, spongioplasm and hyaloplasm. Spongioplasm has a reti. 

 sular or sponge-like arrangement, an affinity for staining fluids, is 

 firmer than the hyaloplasm (but, perhaps, not actually solid), and is, 

 in all probability, highly extensile and elastic. Hyaloplasm, on the 

 3ther hand, is structureless, has little or no affinity for stains, and is 

 lighly labile and fluent. It is by the active flowing of the hyalo- 



