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question we can also give a rather exact answer. It is the adrenals. 
Since long we have known a disease first described in 1855 by 
Appison, and also named after him, the main symptom of which 
is an abnormally strong development of pigment in the skin, so 
that the latter acquires a colour between bronze and dark-brown. 
This pigment is not of haematogeneous origin, for it is without iron, 
as is the skin-pigment of the coloured races. With autopsy of persons 
who have died of this disease, we find, almost without exception, 
degeneration of the adrenals, generally of a tuberculous nature. 
I proceed with another phenomenon. A typical difference between 
man and the other Primates consists in the fact that the sutures of 
the skull in primates close very early. With anthropoids, where they 
remain longest open, they still disappear before the individual is 
adult. In man, on the other hand, the sutures remain much longer, 
and the closing bears more of the character of a symptom of senility. 
The fact of the sutures remaining open is not to be ascribed to the 
considerable development of the brain in man. If this were the case, 
they might also close in man immediately after the termination of 
the growth of the brain, that is, at a comparatively early age. The 
fact of the sutures remaining open in man, is again to be considered 
as the persistence of a foetal character, to which I drew attention, 
a few years ago, in a monograph on this subject. This persistence 
is again the consequence of a _ retardation or suppression of the 
growing-together-process, which manifests itself in the other Primates 
in an earlier or later phase of their development. This process 
consists in the ossification of the fibrous tissue that separated 
the parts of the skeleton, the adjoining parts of the skeleton 
becoming one whole. This ossification-process is retarded in man and 
shifted to a later phase of his life. Even in acentenarian WALDEYER 
found sutures. Now by the influence of which endocrine gland was 
this retardation brought about? The answer to this must be: under 
the influence of Thymus. The significance of this organ is not yet 
known in all respects, but we do know, that it is in the first place 
the skeletogeneous processes in the body which are influenced by 
this gland. 
When thymus is removed experimentally in youthful animals, or 
when this gland has from necessity to be removed surgically in 
young human beings, serious disturbances appear after a short time 
in the ostegeneous processes. Mostly affection of a rachitical nature 
are the result. Now one of the symptoms of rachitis is the so-called 
premature closure of the sutures of the skull, that is to say, the 
sutures disappear even before the individual is adult, sometimes 
