34 PHYSIOLOGICAL CHEMISTRY. 



may be prepared in the same way. 1 The nerve mucin Is prepared 

 from nerves which have first been freed from albumin by common- 

 salt solution and water. They are extracted with lime-water, the 

 filtrate is precipitated with acetic acid, and the precipitate purified 

 by redissolving in dilute alkali or lime-water, precipitating with 

 acid, and washing with water (ROLLETT, LOEBISCH). Lastly, the 

 mucin is treated with alcohol. 



2. Mucoids or Mucinoids. To this group belong pseudomucin, 

 which occurs in ovarial liquids, colloid, which is probably related 

 thereto, and chondromucoid, which occurs in cartilage. These 

 bodies will be treated of later in their respective chapters. 



Hyalogen. Under this name KRUKENBEBG has designated a number of 

 differing protein bodies, which are characterized by the following: By the 

 action of alkalies they change, with the splitting off of sulphur and nitrogen, 

 into a soluble uitrogeuized product called by him hyaline and which yields a 

 pure carbohydrate by further decomposition. Within this group the most 

 widely differing substances may find place, as for instance true mucin and 

 mucoid, the so-called mucin of the holothuria, neossin of the edible bird'snest, 

 the glycoproteid of the vineyard snail, the onuphin and spirographin, and other 

 substances from the lower animals. It is of very little value to collect into 

 one group all these differing substances, which have very little in common, 

 until we have learned with some degree of certainty the nature of the re- 

 ducible substances and other products obtained from them. 



III. Albumoids or Albuminoids. 



iJnder this name we collect into a special group all those pro- 

 tein bodies which cannot be placed in either of the other two 

 groups, although they differ essentially among themselves and from 

 a chemical standpoint do not show any prevailing difference from 

 the ordinary albuminous bodies. The most important and abun- 

 dant of the bodies belonging to this group are important con- 

 stituents of the animal skeleton or the animal structure. They 

 occur as a rule in an insoluble state in the organism, and they are 

 marked in most cases by a great resistance to reagents which dis- 

 solve albumins or to chemical reagents in general. 



The Keratin Group. Keratin is the chief constituent of the 

 horny structure, of the epidermis, of hair, wool, of the nails, hoofs, 

 horns, feathers, of tortoise-shell, etc., etc. Keratin is also found as 

 neurokeratin (KiJHKE) in the brain and nerves. The shell-mem- 

 brane of the hen's egg seems also to contain keratin. 



1 The author has not been able to obtain this pure, so the analysis has 

 not been given in the previous table of the mucins. 



