294 The Structure of Colored Blood- Corpuscles. 



should be sufficient evidence to prove the existence of such a 

 layer to an unbiassed mind." In the colored blood-corpuscles 

 of the frog, he has also seen a distinct stratum, or membran- 

 ous layer. 



"The colored blood-corpuscles of man show a double 

 contour under various circumstances and conditions, indicat- 

 ing the existence, if not of an enveloping membrane, at least 

 of a membranous layer on its surface." As one proof, 

 Schmidt recommends the experiment of pressing down, by 

 means of the point of a forceps, a small round covering glass 

 upon a very small drop of fresh human blood placed upon 

 the slide, "with the object of compressing or crushing the 

 blood-corpuscles as far as possible." " Carefully examined 

 with a first-class objective of sufficient amplification, it will be 

 found that they have not run into each other; but that, on 

 the contrary, the outlines of almost every individual may be 

 discerned, however distorted they may be." 



Almost all investigators nowadays agree that the colored 

 blood-corpuscles of birds, reptiles, amphibia, and fishes, have 

 a nucleus ; while in those of man and other mammalia, except 

 in developmental forms, a nucleus does not occur. On this 

 difference, Gulliver has founded his division of all vertebrate 

 animals into Pyrensemata and Apyrenaemata. 1 But the ex- 

 istence of a nucleus in living] corpuscles of oviparous verte- 

 brata has been denied on the one hand ; while, on the other, 

 the opinion has been advanced that the mammalian red 

 corpuscles, as well as those of other vertebrata, are in reality 

 nucleated. 



'Not to cite older authors, I will mention that Funke* 



(1) " Lectures on the blood of vertebrata" I. c; in " Journal of Anatomy and Physiology, 

 vol. II ; Proceedings of the Zoological Society of February 25, 1862 ; and Hunterian Ora- 

 tion, 1863, referred to in " Observations <jn the sizes and shapes of the red corpuscles of 

 the blood of vertebrates, with drawings of them to a uniform scale, and extended and 

 revised Tables of Measurements." Proceedings of the Zoological Society of London, for 

 the year 1875. Part III, p. 479. 



(2) Lehrbuch der Physiologic Leipzig, 1863, vol. I, p. 17, 



