84 IMMEDIATE PRINCIPLES OF THE TISSUES. 



Mucosine is found in mucus. Three kinds, at least, may be speci- 

 fied ; and Robin and Yerdeil mention five. 1. From the mucous 

 membrane of the nares and bronchial tubes, large intestine, and the 

 interior of the uterus. 2. From the neck of the uterus. 8. In the 

 urine. 



The remaining four substances are, however, of paramount im- 

 portance in histology, and will be particularly considered. They 

 are albumen, caseine, albuminose, and fibrine; the first three of 

 which may be termed the "nitrogenized histogenetic substances." 

 (Lehmann.) 



1. Albumen. 



Albumen is found in the serum of the blood (seralbumen), in the 

 chyle and lymph, in all the serous secretions, the liquor amnii, and 

 the aqueous and vitreous humor of the eye. Of the blood it consti- 

 tutes 63 to 70 parts in 1,000; of the chyle, 30 to 60 ; and of lymph, 

 only 4.34 parts. It exists in the blood in connection with soda, 

 which is supposed by some authors to keep it in its fluid state. The 

 latter is, however, the natural state of this immediate principle. 

 (Robin and Verdeil.) 



Albumen coagulates at a temperature of 145 to 150 (Fahren- 

 heit). If in very dilute solution, however, a boiling heat may be 

 required to solidify it. It is also precipitated from a solution, in a 

 solid form by the tannic, nitric, and all the mineral acids, except the 

 phosphoric. The last, and all the vegetable acids, except the tannic, 

 even dissolve solid albumen. With the former class of acids, and 

 with metallic oxides, the albumen unites as a base, and forms a ni- 

 trate, tannate, &c,, of albumen, though of varying composition. 



But albumen also combines with alkalies and alkaline carbonates 

 as an acid ; these compounds (albuminate of soda, &c.) being soluble 

 in water. The neutral albuminate of soda exists normally in the 

 blood of the hepatic and splenic veins ; the basic in all the other 

 vessels. 



With most of the metallic salts (acetate and other salts of lead, 

 the salts of mercury, &c.) albumen forms insoluble compounds. 



It is coagulated by the ferrocyanide of potassium, by alcohol, and 

 by creasote. The last acts by catalysis. 



Seralbumen contains 2 per cent, of phosphate of lime, besides 

 alkaline and earthy sulphates and phosphates, and chloride of so- 

 dium. Ovalbumen is the form of albumen found in eggs. Of the 



