THE BLOOD. 68i 



When unusually large or superimposed they exhibit the characteristic crimson hue, 

 but when single and small the hemoglobin crystals are colorless or of a faint greenish- 

 vellow tint. On mixing dried blood with a few grains of sodium chloride and a small 

 quantity of acetic acid and heating until bubbles appear, minute brown crystals are 

 formed in large numbers. These are known as Tciclimann s or Jicmin crystals and re- 

 present one of the products derived from the 



reduction of hemoglobin. Being yielded by Fig. 643. 



blood from various sources, they are indica- 

 tive only of the presence of blood and are 

 valueless in differentiating the blood of man 

 from that of other animals. In blood-clots 

 of long standing minute hematoidin oystals 

 often appear as yellowish-red plates. This 



substance is likewise a reduction-product of ll^. \ 1 "1 



hemoglobin. m» ^ » 



The Colored Blood-Cells.— The ma- 

 ture colored blood -cells, erythrocytes, or red ^p> T^^L^-*» ^ 

 corpuscles, of man and other mammals (ex- 

 cept those of the camel family, which are 

 elliptical in outline) are small, biconcave, 

 circular, nonnucleated discs, with smooth 

 contour and rounded edges. When viewed 

 by transmitted light, the individual "red" X.^^ I 

 cells possess a pale greenish-yellow tint, and \ i 

 only when they are collected in masses or 



• , • 1 , • xi J- ^- Crystals of oxyhemoglobin from human 



superimposed m several layers is the distinc- blood. •; 160. 



tive blood-color evident. The peculiar form 



of the corpuscle — biconcave in the centre and biconvex at the periphery — 

 renders accurate focussing of all parts of its broader surface in one plane impossible ; 

 hence under the high amplification necessary for their satisfactory examination, 

 the entire cells are never sharply defined and, according to focal adjustment, 

 appear either as light rings enclosing dark centres or vice versa. Viewed in 

 profile, ?he thicker convex marginal areas are connected by the thinner 

 concave centre, the corpuscle presenting a general figure somewhat resembling 

 a dumb-bell. 



After fresh blood has been distributed as a thin layer and allowed to remain 

 unshaken for some time, the red cells exhibit a peculiar tendency to become arranged 



in columns, with their broad surfaces in contact, similar 

 Fig. 644. to piles or rouleaus of coin (Fig. 646). Agitation dis- 



perses the corpuscles, which, however, may resume their 

 former grouping when again undisturbed. The columns 

 may join one another until a net-work of rouleaus is 

 formed. If the stratum of blood be thin, the red cells 

 usuallv later separate, but they may retain their columnar 

 grouping. 



y " ' ^ M The long-accepted biconcave discoidal form of the mam- 



\^ ^ ,^ ^^ malian erythrocytes has been questioned by Dekhuyzen ' and, 



\., •» ^^. more recently, by Weidenreich '^ and by F. T. Lewis, ^ who be- 



lieve that the normal form of the red blood-cells is cup-shaped, 

 Hemin crystals from human similar to a sphere more or less deeply indented, thus reviving 

 blood. X 250. ^j^g conception held by Leeuwenhoek nearly two centuries ago. 



Although such cupped corpuscles are familiar, they are generally 

 regarded as changed cells resulting from modification of the density of the plasma. The posi- 

 tive testimony of so careful an observer as Lewis as to the occurrence of the cup-shaped red cells 

 within the circulation during Hfe entitle these views to consideration.* 



' Anatomischer Anzeiger, Bd. xv., 1S99. 

 ^ Archiv. f. mikros. Anatom , Bd. Ixi., 1902. 

 ^ Journal of Medical Research, vol. x., 1904. 



■* A critical review concerning the form and structure of the red cells is given by Weiden- 

 reich in Ergebnisse d. Anat. u. Entwick., Bd. xiii., 1904. 



