72 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



Histones. 



Histones are found in the unripe sperm of the salmon [Miescher, 

 1874], mackerel [Bang, 1899], and other fishes [Ehrstrom, 1901] ; also 

 in the ripe sperm of the sea urchin [Matthews, 1897]. The first 

 representative of the group was the histone, to which the name was 

 first applied, prepared by Kossel [1883-84] from the red blood cor- 

 puscles of the goose. Lilienfeld [1894] prepared a similar substance 

 from the thymus, and Schulz [1898] found that globin of haemoglobin 

 belonged to this group. Histones are characterised by being precipi- 

 tated by ammonia in the presence of ammonium salts. Their other 

 properties are described by Bang [1899]. They contain from 15-91- 

 1979 per cent, of nitrogen. 



Histones are supposed to be intermediate compounds between 

 protamines and other proteins, and this supposition is confirmed by 

 the results of analysis. They are distinguished from protamines in 

 their smaller content of di-amino acids, namely, about 25 per cent. 

 Only in the case of thymus-histone has an estimation been made of 

 the mono-amino acids. 



The protein constituent globin of haemoglobin has always been 

 regarded as a histone, but the presence of only 20 per cent, of di-amino 

 acids is against this supposition. Further, the principal di-amino acid 

 is histidine, whereas in the other histones it is arginine. It should be 

 noted that haemoglobin contains a considerably greater amount of 

 histidine than the other proteins. The high content in histidine 

 appears to be a peculiarity of the haemoglobins ;/it may be connected 

 with the origin of the red blood corpuscles from nucleated corpuscles 

 since the glyoxaline ring contained in histidine is also contained in 

 the purine bases, which are present in nucleic acid. Comparative 

 data of the amount of histidine in the haemoglobin of different animals 

 by Abderhalden and Medigreceanu [1909] are at present only avail- 

 able for the red-blood corpuscles; those of the horse contain 5-3 per 

 cent., of the hen 2-8 per cent, of the duck 2-5 per cent., of the goose 

 3-6 per cent. 



An examination of the mono-ammo acids in haemoglobin was 

 undertaken by Proscher [1899] before Fischer had described his ester 

 method. The analysis by Fischer and Abderhalden [1902] was 

 repeated by Abderhalden [1903] whose data were considerably higher 

 than those found by Fischer and Abderhalden ; the mixture of amino 

 acids was esterified three times. Abderhalden and Baumann [1907] 

 analysed the haemoglobin of dog's blood. 



