FIBROUS CONNECTIVE TISSUE. 53 



reprecipitation with 0.2 per cent acid, etc. The content of 

 nitrogen in the three products, when dried at 110 C., was as 

 follows, calculated on the ash-free substance 



First Extract. Second Extract. 



First fraction. Second fraction. 



12.26 N. 11.91 N. 11.61 N. 



It is thus seen that the first extraction with lime-water 

 furnishes a mucin with a considerably higher percentage of 

 nitrogen than the second extract. It is equally noticeable 

 that the mucin first precipitated as in the first fraction of 

 the first extract has a higher percentage of nitrogen than 

 the second fraction, thus indicating that the higher content 

 of nitrogen and probably of carbon also belongs to some body 

 more readily precipitated by acid than the mucin with 11.51 

 per cent of nitrogen. In view of the great care exercised in 

 all of these preparations, and the ready solubility of ordinary 

 forms of albuminous matter in an excess of hydrochloric acid, 

 especially after they have once been dissolved in an alkaline 

 fluid, we are very much inclined to believe in the existence 

 of several related mucins as components of ordinary white 

 fibrillar connective tissue. 



Such a view presents no great difficulty. Submaxillary 

 mucin, for example, differs from tendon mucin by only 0.5 

 per cent of carbon (48.84 per cent) and about 0.5 per cent of 

 nitrogen (12.32 per cent), although it shows some other points 

 of difference, such as a tendency to undergo alteration by the 

 action of lime-water and by being soluble in 0.2 per cent 

 hydrochloric acid. Indeed, all of the various mucins de- 

 scribed show minor points of difference, although agreeing 

 in their general reactions, and it is easy to conceive of the 

 presence of two or more closely related mucins, in tendons, 

 with different elementary composition. 



The most remarkable thing, however, connected with the 

 mucins that we have separated from this form of fibrillar 

 connective tissue is the amount of sulphur present in the 

 purified products. In snail mucin, Hammarsten has shown 



