APPENDIX. 735 



(4.) Fibrin. It is insoluble in water, in dilute saline solutions, or 

 in dilute acids or alkalies; soluble in strong saline solutions (partly) and 

 in strong acids; soluble to a certain extent in strong saline solutions and 

 in gastric or pancreatic fluids. 



(5.) Peptones. These are soluble in water, saline solutions, acids, 

 or alkalies ; they are not coagulated on heating. 



(6.) Coagulated Proteids. These are soluble only in gastric or pan- 

 creatic fluids, forming peptones. 



(7.) Amyloid substance, or Lardacein. This body is generally insol- 

 uble, even in gastric or pancreatic fluids at ordinary temperatures. It 

 gives a brown coloration with iodine. 



CLASS I. NATIVE- ALBUMINS. 



(A) Egg- Albumin is contained in the white of the egg. 

 Properties. When in solution in water it is a transparent, frothy, 



yellowish fluid, neutral or slightly alkaline in reaction. 



It gives all of the general proteid reactions. 



At a temperature not exceeding 40 C. it is dried up into a yellowish 

 transparent, glassy mass, soluble in water. 



At a temperature of 70 0. it is coagulated, i. e., changed into anew 

 substance, coagulated proteid, which is quite insoluble in water. It is 

 coagulated also by the prolonged action of alcohol ; by strong mineral 

 acids, especially by nitric acid, also by tannic acid, or carbolic acid ; by 

 ether the coagulum is soluble in caustic soda. 



It is precipitated without coagulation, i. e., forms an insoluble com- 

 pound with the reagent, soluble on removal of the salt by dialysis, with 

 either mercuric chloride, lead acetate, copper sulphate or silver nitrate, 

 the precipitate being soluble in slight excess of the reagent. 



With strong nitric acid the albumin is precipitated at the point of 

 contact with the acid in the form of a fine white or yellow ring. 



(B) Serum-Albumin is contained in blood serum, lymph, serous, 

 and synovia! fluids, and the tissues generally ; it appears in the urine in 

 the condition known as albuminuria. Two varieties, metalbumin and 

 paralbumin, have been described as existing in dropsical fluids and ova- 

 rian cysts respectively. 



It gives similar reactions to egg-albumin, but differs from it in not 

 being coagulated by ether. It also differs from egg-albumin in not be- 

 ing easily precipitated by hydrochloric acid, and in the precipitate being 

 easily soluble in excess of that acid. Serum-albumin, either in the co- 

 agulated or precipitated form, is more soluble in excess of strong acid 

 than egg-albumin. 



The compound nature of what is usually called serum-albumin, or 

 serine, and its differentiation into three substances, coagulate at differ- 



