54 THE MUCIN OF WHITE 



the presence of 1.75 per cent of sulphur, but in the mucin 

 from the submaxillary gland and in the mucin described by 

 Loebisch as contained in tendons, the amount of sulphur has 

 been placed at 0.84 to 0.81 per cent. In all three of our 

 preparations, however, the sulphur present has amounted to 

 at least 2.30 per cent, and, moreover,' the agreement in the 

 several products has been very close indeed. The greater 

 portion of this sulphur is closely combined, a small amount 

 only being in the form of the mercaptan group and respond- 

 ing to the reaction with potassium hydroxide and plumbic 

 acetate. We present these figures with some doubt in our 

 own minds, but, having obtained them as the result of most 

 careful work, we see no possible explanation other than that 

 this amount of sulphur is actually present in the mucin mole- 

 cule. The determinations of sulphur were made after the 

 usual method recommended by Hammarsten viz., oxidiz- 

 ing the mucin with a mixture of ten grams NaOH and 

 two grams KNO 8 in a silver crucible, etc. The sodium hy- 

 droxide employed was chemically pure, having been prepared 

 from the metal, and, furthermore, several blank tests were 

 made to prove the freedom of the various chemicals from 

 sulphur. This percentage of sulphur is greater than has ever 

 been accredited to a true mucin, although the mucin from 

 the snail's membrane (mantle-mucin), which is somewhat 

 related to keratin, has been found by Hammarsten to con- 

 tain a fairly large amount of this element viz., 1.79 per 

 cent. 



With regard to the reactions of the several products that 

 we have studied, there is nothing special to be said. They 

 all show the ordinary reactions of mucin as described by 

 Loebisch, and we can simply substantiate what has long been 

 published by him upon this point. 



The most characteristic feature of mucin is the peculiar 

 cleavage it undergoes when heated with dilute hydrochloric 

 acid, by which a substance with reducing action upon alkaline 

 copper solution results. Albumose and peptone are likewise 

 formed by the action of the hot acid. We have tried several 



