272 THE DUCTLESS GLANDS 



lin gives it an opaque grey or greyish- violet tinge, and shows a 

 homogeneous or granular structure. The vesicle varies from 

 time to time both as to the amount of the contents and as to 

 their staining reactions, depending upon the state of functional 

 activity of the gland. 



According to Biondi, the vesicles contain a homogeneous 

 substance which becomes dark and granular after fixation with 

 osmic acid. This substance is a product of the epithelial cells, 

 as shown by the fact that these frequently contain granules 

 which have the same staining reaction as the colloid. 



Langendorff was the first to give a clear account of the micro- 

 chemical reactions of the colloid substance. There is no doubt 

 that the contents of the gland vesicles completely fill their 

 interior. If these contents become hard as the result of 

 chemical treatment, they may either preserve their original 

 volume or may undergo change in this respect ; if the harden- 

 ing is the result of dehydration or heat, considerable shrinkage 

 occurs. The best fixing agents are those which coagulate 

 proteins without change of form, such as osmic-acid mixtures. 

 If such be employed, one sees that the masses of colloid lie in 

 close contact with the follicular epithelium, and have a per- 

 fectly homogeneous aspect. Langendorff's micro-chemical 

 tests were carried out upon the gland of the calf and the rabbit, 

 which were hardened in alcohol. Acetic acid caused enormous 

 swelling of the vesicular contents, which were rendered trans- 

 parent. By washing with 0-6 per cent. NaCl one could restore 

 their former appearance. A 0-2 per cent, solution of HC1 also 

 caused this swelling ; 33 per cent. KOH or stronger NaOH 

 has the same effect, only to a much less extent. If, now, water 

 be added, rapid breaking up occurs, and only the connective- 

 tissue framework of the glands remains. A 10 per cent, 

 solution of KOH makes the colloid masses indistinct and 

 deliquescent. Strong HN0 3 causes the masses to shrink some- 

 what ; after some minutes a yellow coloration occurs, even in 

 the cold. This reaction (xanthoproteic) comes on almost 

 instantaneously on heating. Addition of ammonia changes 

 the light yellow tinge into an orange. With pepsin, in presence 

 of 0-2 per cent. HC1, the colloid masses are soon dissolved. 

 Copper sulphate and KOH at 40 C. give a strong violet tinge 

 to the colloid (Biuret reaction). After many hours in the 

 reagent the colloid masses also give Millon's test. If a section 



