BLOOD. 



[ 104 ] 



BLOOD. 



Some methods hare receutly been devised 

 for the enumeration of the blood-corpus- 

 cles. Malassez uses a glass tube, having a 

 capillary bore "with a dilatation near the 

 upper end, in -which is placed a glass 

 globule. To this end is attached an india- 

 rubber tube ; the other end is pointed. The 

 tube is accurately graduated. An artificial 

 serum is made of gum acacia and water, 

 or a saline solution of know^n strength. The 

 point of the tube is then inserted in the 

 blood to be examined, and a certain quan- 

 tity is sucked up. A measure of the serum 

 is then drawn m, and the apparatus well 

 shaken. The corpuscles are thus spread 

 through the serum so as to be diffused and 

 readily counted. For this purpose the 

 mixture is introduced into a capillary tube 

 fixed to a slide, and the number of corpus- 

 cles read oft" by the aid of a micrometer 

 eye-piece. The proportions of the dilution 

 must necessarily be carefully taken into ac- 

 count. The colourless corpuscles can be 

 enumerated in the same manner. Further 

 details will be found in Robin, Mio:, 477 

 (tigs.) ; or Rutherford, Hist., 62 (figs.). 



The colour of the blood of the Vertebrata 

 varies according to whether it is removed 

 from the arteries or the vems, in the former 

 case being of a much lighter and brighter 

 red than in the latter. It is beyond our 

 province to enter into the details of the 

 causes of their difference ; suftice it to say, 

 that it arises principally from an alteration 

 in the globules, by which they are enabled 

 to reflect light more copiously. 



In the Invertebrata the coagulation of 

 the blood is imperfect, and the clot much 

 less firm and copious than in the Verte- 

 brata. 



The uses of the blood scarcely require 

 mention. It is at the same time the nutri- 

 trive fluid from which all the tissues of the 

 body are formed and renovated, and that in 

 which the components of the secretions are 

 produced and from which they are separated. 

 The red particles are subservient to the pur- 

 poses of respiration ; they are most numerous 

 in those animals in which the respiratory 

 function is most active, and which consume 

 the largest proportion of oxygen, as birds 

 and mammalia. 



Development of the Coloured Corpuficks. — 

 In the Vertebrata, two sets of coloured cor- 

 puscles are developed. The first, or embry- 

 onic blood-corpuscles, exist alone, until 

 lymph and chyle begin to be formed, wlieu 

 they are gradually superseded by the second. 



The first blood-corpuscles are formed from 

 colourless nucleated cells with granular con- 

 tents, identical with the formative cells of 

 the embryo, by their losing the granules 

 and becoming filled with haematine. These 

 coloured, nucleated, primary blood-cells, 

 which are spherical, larger and more deeply 

 coloured than the coloured blood-corpuscles 

 of the adult, form, with the colourless for- 

 mative cells, the only elements of the blood. 

 Soon, however, many of them begin to in- 

 crease by division (PI. 49. fig. 3G), becoming 

 elliptical and flattened, and closely resem- 

 bling tlie coloured corpuscles of Reptiles, 

 producingtwo, rarely three or four roundish 

 nuclei, and then becoming resolved into two, 

 three, or four new cells by the formation of 

 one or more annular constrictions. These 

 corpuscles then gradually lose their nuclei, 

 become flattened and excavated laterally, 

 and form perfect coloured corpuscles. 



The formation of the second set, or those 

 produced after birth and in adults, is more 

 obscure. The most probable view appears 

 to be that they are produced from the lymph 

 and chyle-corpuscles, or certain corpuscles 

 in the spleen and liver, by their losing their 

 nuclei, becoming flattened, and producing 

 hfematine. At aU events, corpuscles appa- 

 rently identical with the so-called proper 

 corpuscles of the chyle, siu'rouuded with a 

 membrane which is more or less distended 

 with a red liquid, are met with in the chyle 

 and lymph, and occasionally, but rarely, in 

 the blood itself. Physiologists are not 

 agreed as to the above views ; but the pre- 

 ponderance of evidence appears decidedly 

 in their favour. Recklinghausen has di- 

 rectly observed the conversion of the colom'- 

 less corpuscles of the frog into the coloured 

 corpuscles. 



As unusual constituents of blood, may be 

 mentioned : — 



1 . Cells or masses of protoplasm enclo- 

 sing coloured blood-corpuscles; found in the 

 blood of the spleen, liver, &;c. 



2. Granule-cells, either colourless or con- 

 taining granules of pigment. 



3. Peculiar concentric bodies, three or 

 four times as large as the coloured corpus- 

 cles of the blood, resembling those found in 

 the thymus gland.' 



4. An vm usually large number of colour- 

 less corpuscles in Leucocytha^mia. 



5. Pus-corpuscles. 



0. Caudate cells, sometimes containing 

 pigment. 



7. Crystals of haimatoidine, sometimes 



