SCHULTZ — STERNAL GLAND IN ORANG-UTAN 
195 
infantile, and adult females showing no trace of it. It seems probable, 
therefore, that, while the sternal gland may develop in the female, it 
apparently does so in only a small percentage of cases. Its constant 
presence in males, with the exception of very old animals, and its 
sporadic occurrence in females tends to substantiate the assumption 
that we have to deal here with a secondary sexual character. However, 
the fact that this gland is found as early as the middle of fetal life does 
not conform readily to this theory. 
The sternal pit is most evident in fetuses, where its umbilicated 
opening reaches a diameter of 2.5 mm. The skin patterns are arranged 
in circles around it and become very much finer and smaller immediately 
surrounding it. In juvenile specimens a low circular wall is frequently 
found at the edge of the actual pit. At this age and later most males 
have a round, dark brown pigmented spot, sharply circumscribed, 
with the sternal pit in the center. In the fetus, also, sections show a 
slight increase in pigment at the periphery of the pit, but a large accumu- 
lation of pigment does not occur until later in life. In some instances 
the sternal pit v/as not circular but oblong, in which case the longest 
diameter was always horizontal. Its depth in juvenile specimens was 
in several instances 2 mm. and amounted in one case to even 3.5 mm. 
In old males the pit is very difficult to find, due to the fact that it is 
almost always covered by long hair and hidden among the wrinkles of 
the skin or beneath the folds of the laryngeal pouches. The difficulty 
of detecting the gland in the full-grown animals, where the pit 
also is relatively smaller and shallower than in juvenile and fetal 
specimens, probably accounts for the fact that it has not, so far as 
the author can ascertain, been previously described. An important 
feature of the sternal gland is its constant position, which varies only 
within a few millimeters above or below a line connecting the nipples, 
and which always lies exactly in the midsagittal plane. 
Figure 2 shows a section through the skin containing the sternal 
gland of the fetus shown in figure 1. The sections were cut in a per- 
pendicular direction. One can see a canal emptying into the bottom 
of the spacious pit; beneath lie the large sebaceous glands. A study 
of all the sections showed that a number of these glands have one joint 
outlet, but there are also many others with minor separate openings 
into the pit. The sweat glands surrounding the pit seem to be un- 
usually numerous and of more than average size. In several cases 
microscopically fine hairs can be observed on the edge, and in one 
instance at the bottom of the pit. 
