which extends beyond the concave bone, laid open to show the termination of the Eustachian tube.

h. The internal surface of the Eustachian tube.

i. The opening of the Eustachian tube into the nostril.

PLATE II.

aa. The internal surface of the concave bone.

bb. The fatty case in which it is inclosed.

c. A convexity covered by a thin ligamentous periosteum, whose fibres are radiated and connect the membrana tympani, as well as the membranous fold f, to the bone.

d. The hollow formed on the inside of the membrana

pani.

e. The external surface of the membrana tympani.

tym

f. The membrane stretched across from the concave bone to the malleus.

g. Malleus.

h. Incus.

i. Stapes.

k. Cochlea.

1. Auditory nerve.

m. The bone connecting the petrous portion to the skull. n. A cartilage which had been cut through in preparing the cranium; the part with which the other extremity was connected has not been ascertained.

IV. Chemical Researches on the Blood, and some other Animal Fluids. By William Thomas Brande, Esq. F. R.S. Communicated to the Society for the Improvement of Animal Chemistry, and by them to the Royal Society.

Read November 21, 1811.

SECTION I.

Introduction.

In the following pages I shall have the honour of laying before this Society an account of some experiments upon the blood, which were originally undertaken with a view to ascertain the nature of its colouring matter. The difficulties attendant on the analysis of animal substances have rendered some of the results less decisive than I could have wished, but I trust that the general conclusions to which they lead, will be deemed of sufficient importance to occupy the time of this body.

The existence of iron in the blood was first noticed by MENGHINI, and its peculiar red colour has been more recently attributed to a combination of that metal with phosphoric acid, by M. M. FOURCROY and VAUQUELIN.+ The

VINCENTIUS MENGHINUS de Ferrearum Particularum Progressu in Sanguinem. Comment. Acad. Bonon. T. 2, P. 2, page 475.

Systême des Conn. Chym. Vol. 8, p.

very slight discoloration occasioned by the addition of infusion of galls to a solution of the colouring matter, under circumstances most favourable to the action of that delicate test of iron, first led me to doubt the inferences of those able chemists, and subsequent experiments upon the combinations to which they allude, tended to confirm my suspicion, and induced me to give up no inconsiderable portion of the time which has elapsed since the last meeting of this Society, to the present investigation.

An examination of the chyle and of lymph, in order to compare their composition with that of the blood, formed an important part of this inquiry, especially as those fluids have not hitherto been submitted to any accurate analysis, on account of the difficulty of procuring them in sufficient quantities, and in a state of purity. Whilst engaged in assisting Mr. HOME in his physiological researches, several opportunities occurred of collecting the contents of the thoracic duct under various circumstances, and in different animals; on other occasions Mr. BRODIE has kindly furnished me with the materials for experiment.

SECTION II.

On the Composition of Chyle.

The contents of the thoracic duct are subject to much variation. About four hours after an animal has taken food, provided digestion has not been interrupted, the fluid in the duct may be regarded as pure chyle; it is seen entering by the lacteals in considerable abundance, and is of an uniform white

ness throughout. At longer periods after a meal, the quantity of chyle begins to diminish, the appearance of the fluid in the duct is similar to that of milk and water; and lastly, where the animal has fasted for twenty-four hours or longer, the thoracic duct contains a transparent fluid which is pure lymph.

A. The chyle has the following properties.

1. When collected without any admixture of blood, it is an opaque fluid of a perfectly white colour, without smell, and having a slightly salt taste, accompanied by a degree of

sweetness.

2. The colour of litmus is not affected by it, nor that of paper stained with turmeric, but it slowly changes the blue colour of infusion of violets to green.

3. Its specific gravity is somewhat greater than that of water, but less than that of the blood; this, however, is probably liable to much variation.

4. In about ten minutes after it is removed from the duct, it assumes the appearance of a stiff jelly, which in the course of twenty-four hours gradually separates into two parts, producing a firm and contracted coagulum, surrounded by a transparent colourless fluid. These spontaneous changes, which I have observed in every instance where the chyle was examined at a proper period after taking food, are very similar to the coagulation of the blood and its subsequent separation into serum and crassamentum; they are also retarded and accelerated by similar means.

B. 1. The coagulated portion bears a nearer resemblance to the caseous part of milk than to the fibrine of the blood.

2. It is rapidly dissolved by the caustic and subcarbonated

alkalies. With solutions of potash and soda, it forms pale brown compounds, from which, when recent, a little ammonia is evolved. In liquid ammonia the solution is of a reddish hue.

3. The action of the acids upon these different compounds is attended with nearly similar phenomena, a substance being separated intermediate in its properties between fat and albumen. Nitric acid added in excess redissolves this precipitate in the cold, and sulphuric, muriatic, and acetic acids when boiled upon it for a short time.

4. Neither alcohol nor ether exert any action upon the coagulum of chyle; but of the precipitate from its alkaline solution, they dissolve a small portion, which has the properties of spermaceti: the remainder is coagulated albumen.

5. Sulphuric acid very readily dissolves this coagulum, even when diluted with its weight of water; and with the assistance of heat, it is soluble in a mixture of one part by weight of acid, with four of water; but when the proportion of water is increased to six parts, the dilute acid exerts no action upon it. I was surprised to find that the alkalies produced no precipitation in these sulphuric solutions when heat had been employed in their formation, and where a small proportion only of the coagulum had been dissolved, and was therefore led to examine more particularly the changes which the coagulum had undergone by the action of the acid.

On evaporating a solution of one drachm of the coagulum in two ounces of dilute sulphuric acid (consisting of one part by weight of acid with three of water) down to one ounce, a small quantity of carbonaceous matter separated, and the solution had the following properties.