60 



MANUAL OF HISTOLOGY. 



CHLORIDE OF SODIUM, 



This salt, which is soluble in water, never meets with an opportunity 

 for crystallization within the body, but may be found in crystals upon the 

 surface of the latter under certain circumstances. These crystals (fig. 39) 

 assume the form of dice, frequently marked with step-like depressions on 

 their surfaces, or may be met with in the form of square prisms. Mixed 

 with urea this salt crystallizes in the form of octahedrons, or, according 

 to G. Schmidt, in tetrahedrons also. 



Chloride of sodium, or common salt, is to be found in all animal fluids, 

 and in all the solid parts of the body. Its amount in the juices is variable, 

 but seldom exceeds 0'5 per cent. The fluid which saturates muscle is 

 poorer than any in chloride of sodium. We see also, on the other hand, 

 that though the animal juices may be at one time supplied with a larger 

 quantity of the salt than at another, still the proportion in each fluid is 

 tolerably constant, the surplus passing rapidly out of the body with the 

 urine. The quantity of the substance in question is not less variable in the 



solid portions of the system ; the blood- 

 cells are extremely poor, while cartilage 

 is rich in it. An extremely interesting 

 fact has been pointed out by Bidder and 

 Schmidt, namely, that starving animals 

 very soon cease to void chloride of sodium 

 in their urine, an indication that it is 

 retained by the tissues and juices in the 

 most determined manner as an indispens- 



O^ | __l able ingredient in their composition. 



jjv Some of the discoveries of pathology, 



also, bear out this conclusion, showing, 

 as they do, that during the rapid forma- 

 tion of cells in exudations, the excretion 

 of salt with the urine almost ceases, and 

 that an extraordinary amount of chloride 

 of sodium is required for the plastic process (Heller, Redtenbacher). The 

 experiences we have gathered from observation of domestic animals may 

 also be alluded to here. In them the effect of a greater admixture of the 

 salt in question with their food may be seen in the way it favours the 

 whole process of assimilation (Boussingault). 



All these facts seem to point to the conclusion, that chloride of sodium 

 must be regarded as possessing the nature not only of an aliment, but also 

 of a histogenic ingredient of animal tissue. But as to all the purposes 

 in detail for which it exists in the body, we still possess but a scanty 

 knowledge of them. 



CARBONATE OP SODIUM, Na 2 C0 3 , and NaHC0 3 . 



Carbonate of sodium (the simple as well as the bicarbonate) appears very 

 often in the products of the incineration of animal matters. It cannot 

 be regarded as anything more than a calcination product in this case. 



It is, however, present in several alkaline fluids, as, for instance, in 

 blood, lymph, and the urine of vegetable feeders. In the blood it is the 

 bearer of carbonic acid, and elsewhere the solvent for different protein 

 substances. 



Fig. 39, 



-Different crystalline forms of 

 chloride of sodium. 



