and the skin was of a dark yellowish brown. I saw the child while it was alive, and was struck with its want of growth, and its having no fat under the skin, which made it appear longer than new-born children generally are. Upon examining the body after death, the only mal-formation met with, was there being no gall-bladder, nor any duct leading from the liver into the duodenum.

From what happened in this case, a supply of fat appears necessary for growth, for the child was by no means wasted in its muscles, which it must have been had the constitution not been supplied with nourishment.

Animal fat has, I believe, hitherto been considered as a secretion, although there is no direct evidence in favour of such an opinion. It has nothing in common with the secretions; it is met with in all the interstices of the body; is very often quickly deposited, and in as short a time taken back into the constitution. In these respects it corresponds with the watery fluids, with which the body is supplied.

In a former communication respecting the stomachs of animals, I explained that water was taken up from the stomach by channels yet unknown, and carried into the circulation; from whence it is poured into all the cavities of the body, or thrown out altogether by the kidneys and glands of the skin.

On the present occasion, I hope that I have collected a sufficient body of evidence to prove, that fat is formed in the intestines, and from thence received into the circulation, and deposited in almost every part of the body. When there is a great demand for it, as in youth, for carrying on the growth of the body, it is laid immediately under the skin, or in the

neighbourhood of the abdomen: when not likely to be wanted, as in old age, it is deposited in the interstices of muscles, to make up in bulk for the wasting of the muscular fibres. There appear to be no direct channels by which any superabundance of it can be thrown out of the body, so that when the supply exceeds the consumption, its accumulation becomes a disease, and frequently a very distressing one.

XXII. On the colouring Matter of the black Bronchial Glands and of the black Spots of the Lungs. By George Pearson, M.D. F.R. S.

Read February 25, 1813.

In the adult human animal the glands designated bronchial are generally of a black or dark blue colour. These organs, which are allowed to be lymphatic glands, as is well known, are situated at the root of the lungs externally, within cellular membrane, near the bifurcated trachea; as well as internally on or near the large branches of the bronchi.

At the age of about twenty years the lungs have a mottled, or marbled appearance, from black and dark blue spots, lines, and points disseminated immediately under the transparent pulmonary pleura. As hath been repeatedly observed, the lungs generally become more dark coloured proportionately to their age. Accordingly at upwards of sixty-five or seventy years of life, they often appear almost uniformly black, from the number and congeries, or coalescence of the maculæ, points, and lines just mentioned. Throughout the whole interior substance of the lungs the black spots are seen in a great measure corresponding to the external appearance.

I do not find that any observations and experiments have been made to determine the nature or cause of the black colour above described of the pulmonary organs. It is true, a conjecture has been proposed, that sooty matter taken in with

the air may be the occasion of the colour of the lungs; and that the colour of the glands is occasioned by a peculiar secretion. But the former conjecture has been supposed to be satisfactorily refuted by the absence of the appearance in question among brute animals; as also by its presence in persons who breathe the air of the provinces at a great distance from towns, or places of great consumption of coal; and the latter conjecture is palpably erroneous, because the bronchial glands, of which I am speaking, are not organs of secretion, but of conveyance of lymph.

The course of investigation, in which I have long been engaged, to improve the pathology of pulmonary consumption, led me to some experiments and observations on the subject now stated, which I respectfully submit to the consideration of the Society.

After cutting away the cellular membrane surrounding the black glands, and washing them till the water was no longer coloured, I subjected them to examination.

1. On pressure between the fingers, to burst the investing coat, a black fluid issued which stained the skin, which rendered water black, and which did not alter in colour or apparently dissolve, even at a boiling temperature, either in water or in concentrated muriatic and nitric acids.

2. On breaking down the structure and triturating in a glass mortar a number of these glands with a small proportion of water, a thick black liquid was produced, which was decanted from off many membranous and fibrous masses. But after repeated affusions and trituration, I could not deprive these masses of their black colour, although the water was at last scarcely tinged: it was only by dissolution in caustic potash

lye, or in nitric and muriatic acids, that I could totally separate the black matter from the animal substance to which it seemingly adhered. After repose, a black sediment took place in the waters of elutriation, as well as from the alkaline, and the acid dissolution, which on decantation and evaporation to dryness, afforded the deposit in the state of a black powder.

The texture and proportion of the tingeing matter of the glands was very different in different subjects; whether the lungs, to which they belonged, were in a healthy or diseased condition. In persons of about eighteen to twenty years of age, some of the bronchial glands contained no tingeing black matter at all, but were of a reddish colour; others were streaked, or partially black; and others were quite black, or of a dark blue colour.

3. By boiling the black glands in lye of caustic potash their structure was destroyed, and a turbid black liquid was produced from which, on standing during several days, a copious black sediment took place; but the liquid still remained black, after remaining at rest a month; much of the tingeing matter continuing suspended. By dilution with water, this matter deposited in a clear liquid.

4. By liquid muriatic acid, of the specific gravity 1,170, the bronchial glands were dissolved at a boiling temperature, affording a turbid black liquor; but on repose, an abundant black deposit took place from a clear yellow liquid, as well as a quantity of the same matter appearing on its surface. On separating this precipitate, and evaporating to dryness, it became a black powder.

5. Nitric acid liquid, of the specific gravity 1,500, most speedily dissolved the substances under examination, affording