Influence of Magenta and Tannin on Blood-corpuscles. 67 



to the pigment. The explanation of these appearances presents 

 great difficulties, and in the present state of the inquiry can only be 

 offered provisionally. 



The effect of the magenta-solution is not merely to tint, and so 

 render visible a very minute body. In watching the eflFect of ma- 

 genta, the first thing observed is that the natural yellowish colour of 

 the disk is discharged, and that a faint rose-tint is assumed in its 

 stead. The disks at the same time lose their biconcave shape. The 

 parietal macula is rather " brought out " than revealed, and the 

 action of the solution is, to a very great extent, of a simply osmotic 

 character. 



The action of the tannin-solution is likewise in the main of a 

 similar nature, but modified in some very peculiar manner. Its first 

 operation is to cause the corpuscle to enlarge by imbibition, and this 

 goes on progressively until at length the cell is destroyed. If the 

 solution be strong, this destruction supervenes at once. The tannin 

 also unites with the cell-contents and coagulates them, imparting to 

 the corpuscle, finally, a solid consistence. The conditions of the 

 imbibition are disturbed by the previous application of magenta ; 

 for no pullulation, or at most only traces, occurs when the corpuscles 

 are treated y??**^ with magenta and then with tannin. 



The bearing of these observations on the current views respecting 

 the structure of the vertebrate blood-disk is important. They 

 seem to warrant the inferences drawn in the two following para- 

 graphs : — 



1 . The exact identity of the appearances produced in the blood- 

 disks of the ovipara with those observed in the mammalian corpuscles 

 lends strong support to the view that these corpuscles are homolo- 

 gous as wholes ; and that the mammalian blood-disk is not the 

 homologue of the nucleus of the coloured corpuscle of the ovipara, 

 as was conceived by Mr. "Wharton Jones. 



2. The observations likewise lead to the belief that the envelope 

 of the vertebrate blood-disk is a duplicate membrane ; in other words, 

 that within the outer covering there exists an interior vesicle which 

 encloses the coloured contents, and, in the ovipara, the nucleus. 



Dr. Hensen* of Kiel had already in 1861 convinced himself, from 

 wholly different observations, that the blood-corpuscles of the frog 

 possess such a structure. On this view the blood-corpuscle is 

 anatomically analogous to a vegetable cell, and the inner vesicle 

 corresponds to the primordial utricle. 



The present observations indicate, by direct proof, a duplication at 

 only one, or at most two points in the blood-disks of mammals and 

 birds. Nevertheless certain appearances, occasionally observed, favour 

 the notion of a complete duplication (fig. 1, 6). 



The admission of this hypothesis, however, scarcely removes the 

 difficulties sufficiently to permit a tenable explanation to be offered 

 of the appearances described in this paper. Yet, as it may prove 

 suggestive to some other inquirer, I will not suppress what appears 



* Zeitschrift fiir wissensch., Zoologie, Band xi. p. 263. 



5* 



