438 PRACTICAL PHYSIOLOGY 



the sulphur is an integral part of the molecule. Cystin, when present, 

 belongs to this group. When the relative amounts of S0 3 excreted 

 in the above-mentioned three forms are calculated as percentages of the 

 total SO 3 excretion, it is found that the inorganic sulphates on a protein 

 poor diet behave like urea-nitrogen, i.e. become less both in absolute 

 amount and in relative percentage ; that the neutral sulphur under the 

 same conditions behaves like creatinin-nitrogen, i.e. remains constant 

 in absolute amount, whereas the percentage rises and that the ethereal 

 sulphate excretion behaves like that of ammonia-nitrogen, i.e. becomes 

 somewhat less in absolute amount, but that the percentage rises. 



These facts are clearly shown in the following table, which is an 

 extension of that on page 415. 



N-rich diet. N-poor diet. 



Volume of urine, 1170 c.c. 385 c.c. 



Total nitrogen, - 16 '8 grm. 3 '60 grm. 



Total S0 3 , - - 3-64 grm. 0'76 grm. 



Inorganic S0 3 , - 3 "27 grm. =90'0 % of total S. 0'46 grm. =60 '5 % of total S. 



Ethereal S0 3 , - 0'19grm.= 5'2% O'lO grm. = 13*2% 



Neutral S0 3 , - 048 grm. = 4'8% "20 grm. =26 '3% 



The ethereal sulphates cannot, as has been supposed, derive their 

 source entirely from the aromatic bodies formed in the intestine by 

 micro-organismal growth. When this is excessive, or when there is 

 obstruction in the small intestine so that an excessive amount of these 

 aromatic bodies is absorbed, an increase no doubt occurs in the ethereal 

 sulphate excretion, but this increase can be no reliable index of intes- 

 tinal putrefaction, since the relative ethereal sulphate excretion becomes 

 greater when the diet contains little or no protein. Practically the 

 only source of sulphur intake by the food is in proteins. Sulphates are 

 not taken unless for medicinal purposes, because of their disagreeable 

 taste. The sulphur excretion by the urine is therefore a measure of 

 protein katabolism in the organism. 



URINARY DEPOSITS. 



Normal urine is quite clear when it is passed, but, on standing some 

 time, a sediment usually separates out, and this varies somewhat under 

 different conditions. 



Acid Urine from a healthy person may deposit the following: 

 1. Urates (see p. 424). The sediment has a chalky appearance and is 

 usually tinged reddish by uroerythrin. It disappears on warming the 

 urine. Examined microscopically, it is generally amorphous, but may 

 show a crystalline structure, usually as needles, or as balls with spines 

 projecting from them (Fig. 249). It is composed mainly of sodium 

 urate. 



