CHAP. V 



ALBUMOSES 



181 



Amongst albumoses, only the proto- and the hetero-albumoses, 

 and perhaps also the gluco- and the thio-albumoses, offer some 

 guarantee of purity, while the other albumoses are mixtures. But 

 even the former may not be pure substances, because Pick points out 

 that albumoses, apart from slight differences in their solubilities, have 

 a tendency to unite with one another, forming salt-like compounds 

 (see also the results obtained by Haslam on p. 184), a view which has 

 also been adopted by Haslam. 1 Being amino-acids, albumoses possess 

 both acid and basic characters ; and therefore if several albumoses are 

 present they will keep one another mutually in solution, instead of 

 separating out, as they would do if only one amirio-acid were present. 



A glance at the table on p. 180 will show that the albumoses 

 which have been isolated, so far, show very marked differences both 

 as regards their percentage composition and their disintegration-com- 

 pounds. We know further the following facts : 



Prot-albumose contains, according to Pick, 2 both tyrosin and trypto- 

 phane and some leucin, but no glycocoll, while the hetero-albumose 

 contains phenylalanin and glycocoll, much leucin, but no tryptophane 

 or tyrosin. Hart 3 finds that dissociation with acids yields the 

 following percentage weights : 



Trypsin 3 and erepsin 4 rapidly produce such a change in prot- 

 albumose that it no longer gives the biuret-reaction, while hetero- 

 albumose is not acted upon by trypsin at all, and a slight biuret- 

 reaction is still obtainable, even after four weeks' digestion with erepsin. 

 The ease with which these albumoses dissociate is determined by their 

 chemical constitution ; if we adopt the nomenclature discussed on 

 p. 174 we would class the hetero-albumose and perhaps also the deutero- 

 albumose C under the heading of the anti-group, while the hemi-group 

 would be represented by prot-albumose. A special group is formed by 

 gluco-albumose and peptone A, which are both rich in carbohydrate. 



As such great differences exist between the different albumoses, 

 all the older attempts at determining the percentage composition of 



1 H. C. Haslam, Journ. of Physiol. 32. 267 (1905). 



2 E. P. Pick, Zeitschr. /. physiol. Chem. 28. 219 (1899). 



3 E. Hart, ibid. 33. 247 (1901). 4 0. Cohnheim, ibid. 35. 134 (1902). 



