Development, (&c., of Blood-vessels. By G. and F. E. Iloggan. 577 



moreover, is never found floating within the fat-globule, so that 

 neither chemically nor physically is there any resemblance between 

 the fat-cell and the vacuolating cell. Nor have we ever seen, as 

 stated by Schaefer, a vessel-forming cell of a round form vacuolate 

 and subsequently elongate itself. Without calling his statement in 

 question, we may say that we have never met with even the com- 

 mencement of a vacuole in a vessel-forming cell, until after it had 

 elongated itself and clearly made up its mind to enter into the 

 construction of a blood-vessel. Of course, if the cells are not fixed 

 in the living form by the precaution we have referred to, they are 

 almost certain to retract into the round form. This, indeed, 

 occurred in some of the preparations we made for this research, 

 from which drawings were made before we detected the &ct that 

 the cells had all retracted in the process of preparation ; but here 

 there was no question of subsequent elongation. 



Bearing in mind what we have remarked in the above, let us 

 proceed to trace the process of vacuolation in vessel-forming cells. 

 At i, Fig. 12, we have seen that the vacuole may begin and be 

 formed almost entirely in the substance of the cell protoplasm, 

 and so close to the end of the cell nucleus that, were it not 

 for the other examples, it would be difficult to decide whether 

 or not it touches it. In such a case the nucleus remains evidently 

 undisturbed upon the protoplasm, and the same is true of the 

 nuclei at a and d, Fig. 7. In other cases the vacuole may form so 

 as to sever the connection between nucleus and cell protoplasm, as 

 seems to have taken place in cell g. Fig. 12. In a, Fig. 3, on the 

 other hand, the cell evidently possessed more than one nucleus, or 

 the one nucleus has broken up into its separate constituent bodies, 

 as shown by Pouchet, the one condition in fact being only less 

 advanced than the other. At all events, four bodies are seen 

 within the vacuole, all very much smaller than blood-corpuscles, 

 but one of them, from its staining less intensely than the other 

 three, seems to be fixed or spread out normally on the vacuole wall, 

 or in other words on the cell protoplasm, while the other three 

 appear to be globular in shape and floating loosely within the fluid 

 of the vacuole, whence they would probably float off into the 

 general circulation when connection with it was established. This 

 is possibly the same process as that described by Kanvier and 

 Schaefer, by which blood-corpuscles are formal within cells, a 

 hypothesis, however, the correctness of which we arc not prepared 

 to admit, for those floating bodies are certainly not blood-corpuscles ; 

 and when blood-corpuscles are found within cells or tubes, as in 

 Figs. 13 and IG, we are prepared rather to accent the alternative 

 explanation offered by the former histologist tn£.t such cavities 

 are really retrograding blood-vessels, in portions of which blood' 

 corpuscles have become, so to speak, shut up or imprisoned. 



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