CHEMICAL BASIS OF THE ANIMAL BODY. 1173 



tions (10 p.c. NaCl) are coagulated by heating to 75°. It is 

 readily soluble in 1 p.c. sodium carbonate, is incompletely pre- 

 cipitated from this solution by dilution with water, but fairly 

 completely by the additional passing of a stream of carbon 

 dioxide through the diluted solution. 



Vitellin has not as yet been obtained free from lecithin and is 

 also possibly in egg-yolk: loosely combined with a nuclein. Further 

 investigation is needed to determine its real nature. 



3. Paraglobulin. {Serum-globulin.} 



This proteid occurs most characteristically in blood-serum 

 (also in lymph), in amounts now known to be much larger than 

 was at one time supposed, and thus constituting about one-half 

 of the total proteids of the serum. 



The most satisfactory method of preparing it pure and in 

 considerable quantity is as follows: serum is saturated at 30° 

 with magnesium sulphate, by means of which paraglobulin 

 is quantitatively precipitated. The precipitate collected by 

 filtration is distributed through a small volume of a saturated 

 solution of the magnesium salt, collected on a filter and washed 

 with saturated solution of MgS0 4 . By this means it is sepa- 

 rated from the larger part of the serum-albumin. 



To effect its final and complete separation from this latter 

 proteid, two methods may be adopted, (a) The precipitate is 

 dissolved in water, then largely diluted and the paraglobulin 

 further separated out by passing a stream of C0 2 . (/3) The 

 precipitate is dissolved as before in water, the paraglobulin 

 again salted out by MgS0 4 , this process repeated several times, 

 and the final product separated from the magnesium salt by 

 dialysis. 



Pure paraglobulin is insoluble in water. If dissolved in a 

 minimal amount of alkali it is precipitated by -03 to -5 p.c. of 

 NaCl. On the addition of more than -5 p.c. of the salt it goes 

 again into solution and does not begin to be reprecipitated on 

 the addition of more salt until at least 20 p.c. NaCl has been 

 added. It is not completely precipitated by saturation of its 

 solutions with NaCl. Its dilute saline solutions coagulate on 

 heating to 75°. 



Paraglobulin occurs in smaller amounts Q — |) in chyle, 

 lymph, and serous fluids. 



Cell-globulins. A name given to some forms of globulin which 

 occur in lymph-corpuscles and may be extracted from them by solu- 

 tions of sodium-chloride. Of these, one, cell-globulin-a, occurs in 

 minute quantities only and is characterized by coagulating at 48 — 50°. 

 The other, cell-globulin-/3, is more copiously present in the corpuscles 

 and coagulates in dilute saline solutions at 75°. The latter resembles 

 paraglobulin very closely in properties other than the identity of 



