. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. The History of the Blood-Cellb. We have already seen that the bl« od and the vessels in which it flows have a common origin in the mesoblastic cells of the embryo chick ; the same applies to mammals and lower groups. The main facts may be grouped under two head- ings : 1. Development of the blood-corpuscles during embry- onic Kfe. 2. Development of the corpuscles in post-embryoni
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. The History of the Blood-Cellb. We have already seen that the bl« od and the vessels in which it flows have a common origin in the mesoblastic cells of the embryo chick ; the same applies to mammals and lower groups. The main facts may be grouped under two head- ings : 1. Development of the blood-corpuscles during embry- onic Kfe. 2. Development of the corpuscles in post-embryonic life. The origin and fate of the corpuscles, especially of the colored variety, have been the subject of much discussion. * The best established facts are stated in the summary below, while they are illustrated by the accompanying fig- ures. The colorless cells of the blood first arise as migrated undifPeren- tiated remnants of the early embryonic cell colonies. That they re- main such is seen by their physiological be- havior, to be cqpsidered a little later. Afterward they are chiefly pro- duced from a peculiar Fig. l«.-8nTf«ce view from below of a «niallppr- f^j.^ ^f connective tis- tion of potteriorend of pellucid area of a chicV *"*"* "^ **oi,i»,^ „ of thirty-«ixhourB,l x 400 (Foster and Balfour), gue knOWn aS leucocy- 6. c, blood-corpuaclea; o, nuclei, wlilch iubee- . , u- v. • qnently become nuclei of cells forming walls of tenic, and wnicn 18 ^^STnuiie'l^^tkfCS'u^l^*'""' gathered into organs (lymphatic glands), the chief function of which is to produce these cells, though this is rather widely distributed in the mammalian body in other forms than these. Snnuiuury.—^The student may, with considerable certainty, consider tlid colorless corpuscle of the blood as the most primi- tive; the red, derived either from the white or some form of more specialized cell; the nucleated, as the earlier and more youthful form of t
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