46 Transactions of the 



blood corpuscles, therefore, form the subject treated of in the 

 following pages. 



In the beginning, my examinations, concerning the development 

 of the coloured blood corpuscles, were confined to embryos from six 

 to ten weeks old, in which the circulatory apparatus, judging from 

 the degree of its development, must have been already in full 

 acti^-ity, — and accordingly, the period of the original production 

 of these bodies had passed. For this reason I gained no further 

 information relating to their origin, but became only acquainted 

 with the process of their multiplication. Chance, however, threw 

 into my hands, while I was still engaged in these researches, a 

 human ovum, one half an hour after its expulsion, the diameter of 

 which, including the \illi of the chorion, did not exceed 2^ ctms. 

 This specimen afforded me not only an opportunity to become 

 acquainted with the origin of these blood corpuscles, but disclosed 

 to me also a certain process of multiplication of nuclei, which, as 

 far as I am aware, has not heretofore been observed in the tissues 

 of vertebrated animals. 



When I first saw this ovum, it was enveloped, with the exception 

 of about one-third of its surface, by a clot of blood. On the 

 uncovered portion, an area of about 1^ ctm. in diameter was found, 



the amnion and chorion of the human embryo, 16 mm. in length, mentioned in 

 the text. Magnified 349 diam. 



Fig. 5. — Portion of the wall of the umbilical vesicle of tlie small human ovum, 

 showing the grouping of the follicles ; the light portion between the latter 

 represents the canals. Magnified 49 diam. 



Fig. 6. — Blood corpuscles from the spleen of a human embryo, about twelve 

 weeks old ;— «, mature coloured blood corpuscles ; h, mother-corpuscles, containing 

 but one embrj'0-corpii.scle ; c, an embryo-corpuscle, shortly after its detachment 

 from the mother-substance ; also some young coloured corpuscles of different 

 sizea; d, mother-corpuscles, showing small openings or slits on their surfaces; 

 also another with a large depression, laying on its side ; e, group of very pale 

 disk-shaped corpuscles, probably derived from colourless blood corpuscles; /, 

 groups of free nuclei and colourless blood corpuscles. Magnified 465 diam. ; 

 illuminated with oblique light. 



Fig. 7.— Coloured blood corpuscles from the spleen of a human embryo, about 

 four months old; a ami 6, mother-corpuscles; c, mature; c/, undeveloped with 

 biconvex surfaces. Magnified 4G5 diam. ; illuminated with oblique light. 



Fig. 8. — Blood corpu.scles of the spleen of a human embryo, alx)ut four and 

 a half months old; «, mother-blood corpuscles; 6, remains of old mother-blood 

 corjjuscles ; c, nucleated cells ; d, pale disk-shaped corpuscles. Magnified 720 

 diam. ; illuminated with oblique light. 



Fig. 9. — Elements of the blood, taken from the right auricle of the heart of 

 a human fcetus, about five and a half months old ; a, probably the remains of 

 colourless blood corpuscles, their nuclei being metamorphosed into coloured 

 corpuscles ; a\ similar element with a blood crystal in its centre, met with in the 

 blood of the spleen ; 6, remains of coloured mother-corpuscles, acted on by 

 chromic acid solution. Magnified 720 diam. 



Fig. 10. — a, singular clear, double-contoured cell, attached to a pus corpuscle 

 and containing a coloured blood corpuscle, met with in a specimen of urine 

 containing pus. The enclosed blood corpuscle was seen to turn around its own 

 axis, as described in tlje text ; h, the corpuscle presenting its side, showing its 

 cup-shaped form. Magnified 465 diam. 



