BLOOD. 



[ 103 ] 



BLOOD. 



After setting aside for some hours, it sepa- 

 rates in fine red crystals. Or, on a smaller 

 scale, place a drop of blood on a slide, and 

 add twice as much water, mix the two, and 

 set aside for evaporation. The crystals will 

 then form, often most distinctly at the 

 margins. 



Under very high powers, a number of very 

 delicate, colourless, radiating or reticular 

 filaments may be seen traversing the cor- 

 puscles, sometimes also the nucleus ; pro- 

 bably arising from the coagulation of the 

 contents. 



Carbonic acid causes a cloudiness with 

 enlargement in the red corpuscles, removed 

 by oxygen or air, which also contracts 

 them. 



Electricity produces smaller or larger 

 processes, the corpuscles finally becommg 

 globular and colourless. 



The colourless corpuscles are much less 

 affected by reagents. Water distends them 

 slightly, rendering their granidations less 

 distinct. Acetic acid does the same to a 

 gi-eater extent, bringing to light the nuclei. 

 Alkalies dissolve them. When blood is 

 mixed with a large quantity of water, the 

 mixture shaken and set aside, a pale bufl' 

 precipitate subsides ; this consists of some 

 of the albumen thrown down from the 

 serum, with shreds and walls of ruptured 

 coloured corpuscles, a few of the latter un- 

 altered, and some unaltered or but shghtly 

 changed colourless corpuscles. 



Almost immediately after the blood of 

 the Vertebrata has left the blood-vessels, it 

 begins to coagulate. Within about three 

 minutes, the surface of the coagulating blood 

 becomes gelatinous ; in about ten minutes 

 it is gelatinous throughout; and after a fur- 

 ther lapse of time, the coagulation of the 

 fibrine apparently attains its maximum : 

 this process, however, is not really com- 

 pleted until from twelve to thirty-six hours. 

 We then find a firm red clot immersed in a 

 yellowish liquid. The fibrine during its 

 coagulation entangles a large number of 

 the coi-puscles, which impart to it the red 

 colour ; this is greatest towards the lower 

 part of the clot. The liquid from which 

 the clot has separated, the serum, also con- 

 tains some of the globules in suspension ; 

 most of those not entangled in the clot, 

 however, subside to the bottom of the ves- 

 sel. The sp. gr. of the serum is about 1030. 

 The appearances presented under the micro- 

 scope by a drop of coagulating blood are 

 very interesting. If examined immediately 



I after removal from the body, the cor- 

 puscles are seen to be diffused irregularly 

 over the field ; but after the lapse of about 

 a minute, the red corpuscles unite by their 

 broad surfaces, gradually arranging them- 

 selves into rows resembling strings of figs ; 

 these interlace, forming an irregular red net- 

 work, within the meshes of which the colour- 

 less corpuscles are seen (PL 49. fig. 37). 

 The latter remain isolated, having no ten- 

 dency to unite with the former. To observe 

 these phenomena, the thin glass covering 

 the drop of blood must not be pressed down ; 

 otherwise the free motion of the corpuscles 

 will be impeded. After a time, the fibres 

 break up, and the corpuscles float separately 

 in the serum. 



The coagulated fibrine is also seen dis- 

 tributed over the field, partly in a granular 

 form, but mostly in that of a network of 

 very delicate fibres. Sometimes the running 

 together of the red corpuscles begins to take 

 place immediatelj" the blood has left the 

 body, and the rows are seen to be formed 

 very much more rapidly than in the healthy 

 fluid ; and when this is the case, the upper 

 surface of the clot will be found to be 

 free from the red colour, and more or less 

 cupped or concave : this upper layer is called 

 the huffy coat, and is in general a sign of 

 inflammation. Considerable doubt still 

 exists in regai-d to the nature of this buffy 

 coat. It is also met with in blood which has 

 been covered with a layer of oil before co- 

 agulation. But in the natural state it arises 

 from the subsidence of the corpuscles before 

 the commencement of the solidification of 

 the fibrme, whereby the particles of the 

 latter are brought into closer contact, thus 

 allowing of its greater contraction. Certain 

 salts prevent the separation of the fibrine in 

 the form of fibres, and cause it to assume 

 the form of minute granules or globules. 



In addition to the corpuscles above de- 

 scribed which are constantly found in the 

 blood, it sometimes contains globules of oil, 

 and, after meals especially, two distinct 

 kinds of a white, extremely fine, molecular 

 substance — one consisting of fat, the mole- 

 cular base of the chyle, the other a very finely 

 divided albuminous substance. They render 

 the blood milky in appearance. The dis- 

 tinction of the muscular base of the chyle 

 from the molecidar albuminous deposit must 

 be effected by ether, which dissolves the 

 latter but not the former ; but great care 

 is requisite in judging of the action of 

 ether. 



