376 J. A. MYERS 



Only one supernumerary gland was observed. The second tho- 

 racic glands are those most often absent. 



2. Only one primary duct is present in each gland. This duct 

 after reaching the tela subcutanea turns at right angles and pur- 

 sues a course parallel to the surface of the skin. The majority 

 of the branches of ducts belonging to the first thoracic gland 

 lie cephalad to the nipple, while those from the second and third 

 thoracic glands lie latero-cephalad to the nipple. In case of the 

 abdominal and first inguinal glands the greater number of the 

 ducts lie latero-caudad to the nipples, while in the last inguinal 

 the ducts lie caudad to the nipples. The dichotomous method 

 of branching frequently occurs, especially in the proximal 

 branches. 



3. Reconstructions and cleared preparations show that anas- 

 tomoses sometimes occur between the ducts of a single gland. 

 It is uncertain whether anastomoses occur between the ducts of 

 different glands. 



4. End-buds are present on a large number of terminal ducts 

 at all stages studied. No true alveoli were observed. Large 

 numbers of lateral buds are present on tho sides of all ducts dis- 

 tal to the primary duct during the earlier stages. Such lateral 

 buds later develop into branches of the ducts.' 



5. Considerable individual variation in the development of 

 the glands was noticed. Not only do the corresponding glands 

 of opposite sides differ in their degree of development, but also 

 the glands of one individual may be better developed than those 

 of another even several days older. 



6. The characteristic distribution and ramification of the 

 ducts apparently depend upon the space available for their 

 growth. 



7. The growth and branching of the ducts goes on at an unu- 

 sually rapid rate about the ninth week, probably corresponding 

 to the age of puberty. 



8. A distinct lumen is present at birth in all the ducts distal 

 to the intra-epidermal portion of the primary duct. At the end 

 of the second week the lumen extends to the surface of the 

 nipple. 



