36 MANUAL OF HISTOLOGY. 



Carbolic Acid or Phenol, C 6 H 5 . 



The sources of this compound are manifold, as, for instance, the distil- 

 lation of many organic substances and the oxidation of glue, also, which 

 produces it in traces only. It possesses poisonous properties for the 

 human body. It has been obtained from human and mammalian urine 

 (Staedeler), and met with also, in the same after reception into the 

 stomach of benzol (Schulzen and Naunyn). 



Taurylic Acid or Taurol, C 7 H 8 . 



This second compound, allied to the last, has been obtained from the 

 same fluids, but not as yet in a pure state (Staedeler). It is, perhaps, 

 identical with kressol discovered later. 



G. Nitrogenous Animal Acids. 



25. 



Although from organic chemistry we have learned how to produce a 

 whole series of nitrogenous acids artificially, in a manner reminding us of 

 the alkaloids, the number of such compounds occurring naturally in the 

 Human body is very limited, and none of them have up to the present 

 been composed by art. They are not found in the vegetable kingdom at all. 

 None of these substances possess histogenic properties ; all are and in 

 this respect they resemble animal bases mutation products of histogenic 

 matters or plastic alimentary materials. Owing to their complex constitu- 

 tion they give rise, under certain circumstances, to chemically interesting 

 mutations. If we except two less- known acids which are met with in 



muscle and sweat, they are either constituents 

 of the urine or the bile, forming essential 

 elements of these secretions. 



Inosinic Acid, C, H 14 N 4 O n . 



This is a non-cry stallizable acid, met with 

 in the form of a syrupy fluid, whose constitu- 

 tion is not yet quite certain. It is a constituent 

 of muscle-juice, and as such probably a muta- 

 tion product of the fleshy fibre. 



Hydrotinic Acid. 



This is likewise a syrupy acid, recognised 

 by Favre as a constituent of human sweat. 



Uric Acid, C 5 H 4 N 4 O 8 . 



Fip.13. Uric acid in its various crys- _. . , .. . , 



taiune forms, a, a, a, crystals such Inis Dibasic acid, a derivative ot ammonia, 



as are met with on the decomposi- Qrir | n f 11T1 Vnnwn pnnofifntirm annoara fr fh 

 tion of urates ; 6, crystalline forms and Ol Unknown Constitution, appears to tne 



from human urine; c, dumb-beii unaided eye as a white powdery or scaly 

 substance. Under the microscope the greatest 



variety in crystalline form, may be seen in uric acid. By the splitting up 

 of the salts of uric acid we obtain rhombic tables, or six-sided plates 

 (fig. 13, a, a, ) resembling cystin. Precipitated very slowly, uric acid 

 forms elongated right-angled tables, or parallelopipedic figures, or even 

 right-angled, four-sided prisms with straight ends. The latter are often 



