Some of his later researches indicate that a substance is to be found, under certain circumstances, which has its origin in the cells of the medulla, and is secreted by them as well as by the lymphatics and blood-vessels. This substance is a colloid of an albuminous character, and Dr. Auld believes that it is essential to the well-being of the blood.
Dr. MacMunn, of Wolverhampton,' has made spectroscopic exam inations of the cortex and medulla of the adrenals of many animals. In the former he finds the spectrum of histohmmatin, in the latter that of htemochromogen. The latter substance he considers to be excretory, and he finds it only in the bile and iu the liver. He thus regards the medullary portion of the adrenals as potential for meta morphosis of effete haemoglobin or hrematin into hEemochromogen, and suggests that disease of this portion, or removal of it, May entail retention of effete pigment with dispersion or deposit of it in the skin or mucous membranes, or the urine. This is an interesting con ception, but it cannot come to our aid with an explanation of the fact that several destructive diseases of the adrenals are quite imaccom panied by the peculiar melasma or pigmentary staining of true Addi son's disease.
' Dr. MacMunu refers to embryological researches on the adrenals, and quotes Balfour's and Mitsukuri's observations showing that the medullary portion is developed from the sympathetic ganglia, and the cortex from the mesoblast. The former is at first external, but becomes ultimately invested by the latter, although retaining connec tion with the neighboring ganglia. The bulk of the organ is cortical, and being of mesoblastic origin may be considered as essentially glan dular in nature. The extraordinary wealth of blood-vessels is indi cative of important functions, and no less is the distribution of the lymphatics, which, according to Klein, is significant of their carrying off some product of the metabolic activity of the glands, for it has been shown that the pigment formed in them is conveyed to the lymph glands which lie in their path. These researches all Point to the fact that the adrenals are blood-metabolizing glands. They appear to remove from the circulation useless and worn-out pigments and their accompanying proteids.