BLOOD. 



[ lor, ] 



BLOOD. 



witliin tlio coloured corpuscles, at others 

 free ; also crystals of licemoglobine (lipe- 

 luatoglobuliiie). 



8. The two molecular substances previ- 

 ously mentioned. 



9. Ilreniatozoa. Filaria hominis; other 

 species in the deer, dog, rat, &c. ; Bilharzia. 



10. ITfematophyta. Bacteria, Bacilli ; 

 Sjnrochcrfc (relapsing fever). 



1 1 . Altered colouring matter of the blood, 

 forming minute rounded or angular black 

 particles, contained in the colourless cor- 

 puscles ; in splenic disease, and malaria. 



It sometimes becomes of importance to 

 be enabled to determine the presence of 

 blood in supposed blood-spots, &c., and to 

 distinguish that of man from that of ani- 

 mals. As regards the former point, it is a 

 matter of no great difficulty. When blood 

 has been dried at ordinary temperatures, 

 the dried serum and contents of the cor- 

 puscles redissolve on digestion with cold 

 water; and this is the condition under 

 which the blood is generally presented for 

 examination in such cases. We then have 

 the fibrine left undissolved, which may be 

 tested as to its chemical and microscopical 

 characters (Fibmne). The Uquid is de- 

 colorized by boiling, and the coagulum as- 

 siunes a brown colour (H^mati^'e). It 

 also contains iron, is unaltered in colour by 

 solution of potash, and contains a proteine 

 compound. In heating very minute quan- 

 tities upon a glass slide, the liquid must 

 always be covered with a slip of thin glass, 

 to prevent its drying. The mere presence 

 of blood can thus be chemically determined 

 without much difficulty; for these reac- 

 tions may be obsened under the micro- 

 scope in a very miniite quantity ; but the 

 distinction of small quantities of the blood 

 of man from that of animals by chemical 

 means, is impossible. We have therefore 

 only the morphology of the elements or 

 the spectral analysis to decide from. The 

 portions of blood presented for examination 

 will be almost invariably in a dried state ; 

 and the red corpuscles, when dried in a very 

 thin layer, retain so nearly their natui'al 

 size and outline, that any kinds of blood 

 which are distinguishal^le in the fresh state, 

 are certainly so when dried ; but it will 

 seldom happen that the blood Avill be dried 

 upon a transparent substance, and in thin 

 layers, permitting of its examination by 

 transmitted light. It must therefore be 

 separated from some fabric or structure, and 

 restored as nearly as possible to its original 



appearance. This can be done b}^ digesting 

 the blood in a solution of bichloride of mer- 

 cury, Kobin's liquid fp. lOU), or a f-l-p. c. 

 salt-solution, and placing it under a bell- 

 glass for some hours; the red corpuscles may 

 then be detached with a camel's-Jiair pencil, 

 and examined. Of com-se, only those cor- 

 puscles should be measured which evidently 

 retain their natural form. The red corpuscles 

 of the mammalia are readily distinguishable 

 from those of the lower classes in the animal 

 kingdom by their circular diseoidal form and 

 the absence of a nucleus ; but those of indi- 

 vidual groups can only be recognized by a 

 difference in size. And great difference of 

 opinion exists as to whether the blood-cor- 

 puscles of man can be distinguished from 

 those of other animals. This point has been 

 particularly discussed by Richardson, Am, 

 Jn. Med. Sc. 1874, 102 (3/. M. Jn. 1874, 

 xii. 130) ; and Woodward, 31. M. Jn. 1875, 

 xiii. 65. 



Virchow recommends that the blood-spots 

 be mixed with dried and powdered chloride 

 of sodium ; next, that glacial acetic acid be 

 added, and the mixture evaporated at 212°, 

 when the blood-crystals (chloride of hsema- 

 tine) are abundantly deposited. 



We should recommend those who are 

 likely to undertake such investigations to 

 make their own table of sizes ; for it curi- 

 ously happens that in general the size of 

 the same objects given by different observers 

 varies considerably. This arises probably 

 from using too low a power, want of practice, 

 and the use of a false standard. And we 

 should not advise anj-one to attempt to form 

 a judgment in a judicial question of this 

 kind except he be thoroughly acquainted 

 with the use of the microscope and micro- 

 metric investigations and the most difficidt 

 spectroscope, and has made numerous ex- 

 periments upon this special point. 



The corpuscles of the blood are best stu- 

 died while existing in the serum of that 

 liquid; butthe white of egg neutralized with 

 acetic acid exerts but little action upon them, 

 as is also the case with a solution of bichlo- 

 ride of mercury. The colourless corpuscles 

 are most easily recognized when the blood 

 has been mixed with water. 



They are best preserved when dried in a 

 very thin layer upon a slide— a drop of blood 

 being placed upon the slide, and the latter 

 placed in a perpendicular position, so that a 

 very thin layer will remain ; in the liquid 

 state, a solution of 1 part of bichloride ot 

 mercury, and 2 of chloride of sodium, in 



