THE DUCTLESS GLANDS 1193 



recovered from the urine. It is possible that the polyuria, which is not 

 infrequently observed in association with head injuries or tumours of the 

 brain, may be occasioned by an increased escape of this material into the 

 general circulation. 



Extracts from the anterior lobe have no definite effect when injected 

 into the blood-stream. Schafer found that the addition of the anterior 

 lobe of the pituitary body to the food of young growing animals causes 

 an increased rate of growth. In this experiment eight rats of a litter 

 were taken : four were fed with bread and milk to which the anterior lobes 

 of pituitary bodies had been added, while the other four, which served as 

 controls, received bread and milk with a corresponding quantity of testis or 

 ovary. Later experiments have not however confirmed these results. 

 According to Mackenzie extracts of the pituitary body have a marked 

 excitatory effect on the secretion of milk by the mammary glands. 



It is evident that much further work is necessary before we can regard 

 the functions of the pituitary body as definitely ascertained. The evidence 

 we have at present would seem to point to the following conclusions : 



(a) The anterior lobe furnishes some substance to the circulation which 

 promotes growth, especially of the bony and connective tissues of the body. 



(6) The intermediate part surrounding the cleft between anterior and 

 posterior lobes, in addition to the production of some substance which is a 

 general excitant for unstriated muscle and produces diuresis, also furnishes 

 a colloid secretion which passes directly into the ventricles of the brain and 

 may be assumed to have some influence on the growth or functions of the 

 central nervous system. Schafer regards the principle giving rise to diuresis 

 as distinct from that causing contraction of unstriated muscle, since diuresis 

 may occur without corresponding rise of blood-pressure. The independence 

 of the two phenomena, renal and vascular, cannot be regarded as proved. 



(c) The posterior lobe consists mainly of neuroglia. We have no clue to its 

 functions apart from the masses of intermediate cells which it may contain. 



Very little can be said as to the other ductless glands. The thymus 

 forms two large masses in the anterior mediastinum which in man grow up 

 to the second year of life and then rapidly diminish so that only traces 

 are to be found at puberty. It contains a large amount of lymphatic tissue 

 and is therefore often associated with the lymphatic glands as the seat of 

 formation of lymph- corpuscles. The epithelial remains of Hassell's cor- 

 puscles found in the medullary part of its globules have not had any func- 

 tion assigned to them. In certain cases of arrested development or of 

 general weakness in young people the thymus has been found to be per- 

 sistent. The effect of extracts made from the thymus do not differ from 

 those of extracts made from any other cellular organ. 



The pineal gland has, so far, not been proved to have any function in 

 metabolism.* It is interesting as a vestigial remnant of a primitive 

 dorsal eye. In certain lizards this organ still presents traces of its original 



* Cases have been recorded in which tumours of the pineal body have been asso- 

 ciated with obesity, premature sexual development and early maturity. 



38* 



