. Elements of histology. Histology. 2o Elemexts of Histology. in constitutional chronic diseases the number of red corpuscles is, as a rale, decreased; so also in anj^mia, spontaneous or following acute infectious diseases, fevers, etc. The number of white corpuscles is always greater after a copious meal than during fasting. Certain diseases are associated with a decrease, others an increase, of the white corpuscles of the cir- culating blood; the decrease when pronounced is spoken of as leucopenia^ the increase as leucocy- th(emia^ leucctmia, or leucocytosis. 10. The red blood corpuscl
. Elements of histology. Histology. 2o Elemexts of Histology. in constitutional chronic diseases the number of red corpuscles is, as a rale, decreased; so also in anj^mia, spontaneous or following acute infectious diseases, fevers, etc. The number of white corpuscles is always greater after a copious meal than during fasting. Certain diseases are associated with a decrease, others an increase, of the white corpuscles of the cir- culating blood; the decrease when pronounced is spoken of as leucopenia^ the increase as leucocy- th(emia^ leucctmia, or leucocytosis. 10. The red blood corpuscles (Fig. 13) of man and mammals are homogeneous bi-concave discs (ex- cept in the camelida?, where they are elliptical), and do not possess any surroundmg membrane or nucleus. Being bi-concave in shape, they are thinner and more transparent in the centre than at the periphery. In other vertebrates they are oval, and more or less flattened from side to side, and each possesses a central oval nucleus. The diameter of Fig. 13.â^arious kiuds of Red Blood i , i i i i Corpuscles. the human red blood A, Two human, one seen flat, the other COrpUScle is about edgeways; b, a red corpuscle of the â â p " 1 ' camel; c, two red corpuscles of the solTo '^^^ mCll 111 frog, one seen from the liroad, the \ â \,\ â i , other from the narrow side. DreaCltn, aOOUt 7 "8 ^. and its thick- ness about ^ ^QQQ of an inch. But there are always corpuscles present which are much smaller by about one-third to one-half than the othersâmicrocytes. In normal blood these microcytes are scarce : but in certain abnormal conditions, especially in pernicious anfemia, they are conspicuous by their number. According to Gulliver, ^A'elcker, and others, tlie followinof are the averagfe diameters of the red blood corpuscles of various vertebrates : Man, -3-2V0 J ^^i 08 A. "3'sou ' ^"^j 4cFo^ y outc|7, 5000^ } ;^jii«., :jTi 5" ^ 1 ⢠cat, ^J^; sheep, ^^W i elephant,. Pl
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