ORIGIN OF COLORED BLOOD-CORPUSCLES. 105 



corpuscles have nuclei. The nucleus is evidently not a require- 

 ment of juvenile red blood-corpuscles. 



"In full-grown birds such a new formation of blood-cor- 

 puscles does not occur. In a pigeon nine months old, the layer 

 of globular cartilage-corpuscles is directly bounded by bone- 

 tissue, containing medullary spaces tilled with fat. The blood- 

 vessels of these spaces at their upper ends, looking toward the 

 cartilage, are looped. The intermediate stage of ossification of the 

 basis-substance and new formation of blood-vessels and haemato- 

 blasts is absent. In still older animals, in which the layer of 

 hyaline cartilage is much reduced in thickness, the upper ends of 

 the medullary spaces toward the cartilage are closed by concentric 

 systems of lamellae of completely formed bone-tissue." 



Hayem (see page 98) in 1877 described small shining lumps 

 in the fluid of blood, more numerous in the foetus than in the 

 adult, which he, I think justly, termed " haematoblasts." 



Red blood-corpuscles are very early formations of the middle 

 layer (mesoblast) of the embryo. Probably they originate in 

 every part of the body wherever there is living matter, especially 

 in all varieties of that tissue which is exclusively supplied with 

 blood-vessels, viz. : the connective tissue. Red blood-corpuscles 

 are produced from lumps of living matter whenever, in the young, 

 one variety of connective tissue is transformed into another f . i., 

 cartilage into bone. After the organism has reached full develop- 

 ment, the production of colored blood-corpuscles continues in 

 that variety of connective tissue which longer than any other 

 remains in a juvenile condition, namely, the lymph-tissue. This 

 tissue is present in large quantity in the body the larger the 

 younger the individual. It exists in all mucous layers, in the 

 medulla of juvenile bone, in the lymph-ganglia, and in the spleen. 

 Unfortunately, in consequence of former misapprehension of the 

 nature and significance of this tissue, it bears the misnomer 

 "adenoid tissue.' 7 That this tissue is a source of red blood- 

 corpuscles during the entire life-time, will be demonstrated in the 

 next article. 



EXPERIMENTAL AND MICROSCOPICAL STUDIES ON THE ORIGIN OF THE BLOOD- 

 GLOBULES. BY A. W. JOHNSTONE, M. D., DANVILLE, KY.* 



The objects of this paper are to give the result of a repetition of Onimus's 

 experiments on the " origin of the white blood-corpuscles," and to place on 

 record an account of an undescribed method of development that is constantly 



* " Archives of Medicine," vol. vi.. August, 1881. 



