164 BASIC BODIES. 



The urea is possibly only excreted in increased quantity when 

 material for its formation is sufficiently supplied ; now if poly- 

 phagia be not combined with this urea-diathesis,, the source of the 

 urea must be sought in the waste or consumption of the nitro- 

 genous tissues ; this is not based on the tendency of the tissues to 

 be converted into urea, but depends on other processes which 

 accompany many morbid processes. In diseases where such a 

 consumption actually occurs, I have never found the urea passed 

 in twenty-four hours exceed the normal quantity, and have very 

 often found it far beneath the average. 



A diminution in the amount of urea excreted during disease 

 in twenty-four hours is very frequently observed: this, however, 

 in most cases, may be dependent on the low diet. 



Becquerel has made the best observations in reference to this 

 subject ; it appears, however, to us, that such investigations may 

 rather serve to enable us to form an opinion of the morbid process 

 in a special case, than to establish general rules regarding the di- 

 minution of the urea in the urine in certain classes of disease. 



It is by careful observation of the urine in individual cases, 

 and not by drawing general inferences, that we can make these 

 examinations useful. 



Many chemists have long sought in vain to detect urea in nor- 

 mal blood ; Simon believed that he had found it in calves 5 blood, 

 and Strahl and Lieberkiihn,* and recently Garrod,f maintain that 

 they have detected it in human blood : without doubting the cor- 

 rectness of the observations of these chemists, it is only recently 

 that I have been able to convince myself with precision by deci- 

 sive experiments that urea is present in normal blood. 



In my investigations regarding the amount of alkaline carbon- 

 ates contained in the blood, I often operated on four or six pounds 

 of fresh ox -blood : in order to avoid the decomposition and re-ar- 

 rangement of the soluble mineral constituents of blood which always 

 occur in ordinary incineration, I first separated the coagulable 

 matters of the blood, after diluting it with four times its volume of 

 water, and neutralising it with acetic acid ; the residue left by the 

 evaporation of the fluid, from which the coagulated albumen had 

 been removed by filtration, and the films that formed during 

 evaporation had been skimmed off, was treated with absolute 

 alcohol, and then, in the manner we have already described, 

 examined for urea ; the measurements of the angles of the crystals 



* Preuss. Vereins-Zeit. No. 47, 1847. 



t Medico-Chirurgical Transactions. Vol. 31, p. 83. 



