212 



THE AMERICAN MONTHLY 



[November, 



those of adult life, and appear at 

 the same time as the vessels and 

 heart. The cells of the mesoblast, 

 from which these are developed, 

 are called ' embryonic cells,' and 

 are granular and spherical. From 

 them the most widely differentiated 

 tissues are developed. Each one 

 appears to have its peculiar mode 

 of expression of vitality impressed 

 upon it, and hence some go to form 

 connective tissue, and others the 

 embryonic nucleated red corpuscle. 

 In their development into the latter 

 they become clearer, and are slightly 

 tinged with haemoglobin. At the 

 same time that this formation is oc- 

 curring, lymph-corpuscles are pour- 

 ing into the circulation from the 

 lympathic glands. As seen by 

 Remak in the embryo fowl, the 

 nucleated red multiply partly by 

 division. Kolliker noticed the same 

 thing in the mammal (the rabbit] ; 

 so did Frey and Paget. When, m 

 the development of the embryo, the 

 lymph-corpuscles appear and are 

 added to the blood, they supersede 

 the embryo-coi-puscles ; and it is 

 noticeable that this occurs in the 

 frog at the time of the disappea- 

 rance of the external branchial, and 

 in the chick by the closure of the 

 visceral branchial clefts. Kolliker, 

 confirmed by Weber, asserts that 

 this transformation into red nucle- 

 ated cells can occur in very early 

 foetal life throughout the entire 

 circulation, but of course, ceases 

 when the true white corpuscles and 

 the non-nucleated red ones appear. 

 The nucleated red are lost sight of 

 about the third to fifth month of 

 foetal life in man, though the exact 

 time is not definitely known. 



" Thus, it is evident that there are 

 two sets of red corpuscles in man 

 and mammalia — a temporary em- 

 bryonic set, which are globular and 

 have nuclei, and a permanent ma- 

 ture set devoid of nuclei, but bi- 



concave. * * * Besides these 

 red, we have also the common white 

 corpuscles. Hence, it seems evident 

 to us that we cannot but be prepar- 

 ed to recognize the embryonic set 

 of red corpuscles of mammalia as 

 the analogues of the mature set of 

 red corpuscles of oviparous verte- 

 brates, while the colorless or primo- 

 genial corpuscles are analogous to 

 the pale globules of the blood of 

 adult vertebrates, and to the pre- 

 vailing or characteristic corpuscles 

 of the blood of many vertebrates. 

 This sustains the fact of a temporary 

 structure (red nucleated embryo 

 corpuscle) in the mammalia, corres- 

 ponding to a permanent one in the 

 ovipara ; so that, in its course toward 

 the highest type, there are tem- 

 porary phases in which the blood 

 of the mammal is analogous to the 

 permanent state of the blood of 

 oviparous vertebrates and of inver- 

 tebrate animals, ■s^ * * 



"After stating that the white 

 corpuscles originate in the Ij'mpha- 

 tics and the spleen, the author 

 proceeds to explain the origin of 

 the red cells : " To Neumann, of 

 Konigsberg, belongs the credit of 

 having thrown light upon the sub- 

 ject, and also of having inaugurated 

 investigations which have proved 

 of direct benefit to our knowledge 

 of disease. He claimed the marrow 

 of the bones to be an organ involved 

 in the formation of blood-cells. 

 * * * Capillary vessels are in 

 this tissue, their meshes being twice 

 the diameter of the capillary vessels 

 around them. The meshes have 

 rounded angles, and are polygonal 

 in shape. They are more numerous 

 next to the bone than at the other 

 parts of the tissue. The finest 

 capillaries found in the marrow he 

 stated to have this peculiarity, that 

 they are larger than the ultimate 

 capillaries of the periosteal and 

 osseous network. In the spongy 



