TISSUES OF THE BODY. 



Ill 



nothing of the usual central depressions ; they resist for a comparatively 

 long space of time also the action of water. Similar cells also make their 

 appearance in the spleen (FunJce). They are looked upon by some as 

 young newly-formed blood-corpuscles. 



REMARKS. Beale in the "Quarterly Journal of Microscop. Science," 1864. 

 Transact, p. 32. 



68. 



The study of the coloured cells of the blood of other vertebrates, as a means 

 of controlling the results obtained in the investigation of those of human 

 blood, is of great interest, and a chapter of comparative histology which 

 cannot, therefore, be completely passed over here. 



The blood-corpuscles of mammalia present almost unexceptionally the 

 form of biconcave disks (fig. 113, 1), and the only slight variations in 

 them are those of size. Thus the cells of the elephant, which are the 

 largest, attain a diameter of about 0*0095 mm., those of apes correspond 

 with the human cells, and in many other mammals they are smaller than 

 our own, as, for instance, in the horse, 0'0056 mm., and rabbit, 0*0080 mm. 

 The blood-cells, however, of some of the ruminants, as of the lama, alpaca, 

 and camel, show striking deviations, being oval disks of O'OOSl mm. Of 

 nuclei, we see just as little in the coloured elements of mature mammal 

 blood as in those of our own. 



Such elliptical blood-cells, however, become the prevailing form in the 

 succeeding classes of vertebrates, manifesting, moreover, striking varia- 

 tions in size; and the nucleus, which we have missed up to this, now 

 takes its place as a regu- 

 lar constituent of the 

 cell. It is only in a low 

 order of fishes, the cyc- 

 lostomata, that the cir- 

 cular figure of the mam- 

 mal cell is found again ; 

 and the lowest of all ver- 

 tebrates, the extraor- 

 dinary Amphyoxus lan- 

 ceolatm, possesses com- 

 pletely anomalous blood, 

 no longer red in colour, 

 and reminding us of that 

 of invertebrates : it need 

 detain us no longer here. 



The corpuscles of 

 birds have an average 

 length of 0-0184- 

 0*0150 mm., and trans- 

 verse diameter amount- 

 ing to the half of this 

 (a a) (fig. 113, 3). 



Seen from the side, instead of the biconcave disk, they present a bulging 

 out in the central portion of each surface. The nucleus, which in uninj ured 

 cells is either not at all visible, or only so as a slight clouding, appears on 

 proper manipulation, e.g., desiccation, or the action of water, &c., as 

 a dark structure with rough contour, elongated figure, and diameter of 



Fig. 113. Coloured blood-corpuscles. 1, From the human being ; 

 2, camel; 3, dove; 4, proteus; 5, water salamander; 6, frog; 

 7, cobitis ; 8, ammocoetus. At a, views in profile ; &, from the 

 edge (mostly after Wagner). 



