454 THE BLOOD [cii. XXIX. 



C. Salts. The most abundant salt is sodium chloride; it con- 

 stitutes between 60 and 90 per cent, of the total mineral matter. 

 Potassium chloride is present in much smaller amount. It consti- 

 tutes about 4 per cent, of the total ash. The other salts are 

 phosphates and sulphates. 



Schmidt gives the following table : 



1000 parts of plasma yield 



Mineral matter ......... 8*550 



Chlorine 3-640 



SO 3 0-115 



P 2 O 5 0-191 



Potassium 0-323 



Sodium 3-341 



Calcium phosphate 0*311 



Magnesium phosphate 0-222 



The Blood- Corpuscles. 



Red or Coloured Corpuscles. Human red blood -corpuscles are 

 circular biconcave discs with rounded edges, -g^Vo inch in diameter 

 (7 JUL to 8 JUL) and T 2ihro- inch, or about 2 /z, in thickness. When viewed 

 singly they appear of a pale yellowish tinge ; the deep red colour 

 which they give to the blood is observable in them only when they 

 are seen en masse. 



According to Rollett they are composed of a transparent filmy framework 

 infiltrated in all parts by the red pigment haemoglobin. This stroma is elastic, so 

 that as the corpuscles circulate, they admit of change in form, and recover their 

 natural shape as soon as they escape from compression. According to this theory, 

 the consistency of the peripheral part of the stroma is greater than that of the 

 central portions ; the outer layer thus plays the part of a membrane in the processes 

 of osmosis that occur when water or salt solutions are added to the corpuscles. 

 This view of Rollett has been questioned, particularly by Schafer, who regards the 

 red corpuscles as composed of a colourless envelope enclosing a solution of haemo- 

 globin. The presence of a membrane on the exterior of the corpuscle is undoubted, 

 and can be clearly distinguished by a good microscope in the larger corpuscles of 

 amphibia. It is, however, difficult to explain the elasticity of the corpuscles, and 

 the central position of the nucleus in nucleated red corpuscles, unless we also assume 

 that delicate fibres pass across the interior of the corpuscles. 



The red corpuscles of other mammals are generally very nearly 

 the size of human red corpuscles. They are smallest in the deer 

 tribe and largest in the elephant. In the camelidae they are 

 biconvex. In all mammals the corpuscles are non-nucleated, and 

 in all other vertebrates (birds, reptiles, amphibia, and fishes) the 

 corpuscles are oval, biconvex, and nucleated (fig. 319), and larger 

 than in mammals. They are largest of all in certain amphibians 

 (amphiuma, proteus). 



A property of the red corpuscles, which is exaggerated in inflam- 

 matory blood, is a tendency to adhere together in rolls or columns 

 (rouleaux), like piles of coins. These rolls quickly fasten together 



