peculiar condition of the skin was only one of the

effects or symptoms..

There are many facts that appear to prove, that the skin emits a peculiar odorous matter, by means of which dogs, and other animals that possess a delicate scent, are enabled to detect the presence of other animals, or to trace them out for long distances. We have, perhaps, no decisive means of ascertaining whether this odorous effluvium depends upon the perspiration itself, or upon some other secretion which is mixed with it, and discharged from the body along with the perspirable matter. Upon the whole, however, it is probable that they are distinct substances, that the proper matter of perspiration is produced from every part of the surface, and is nearly or altogether without odour, while there are certain parts of the body which are provided with glands, that secrete a peculiar or specific substance, which composes the odoriferous effluvium. This latter would appear to be of an oily nature, and will therefore belong to a different class..

The perspirable matter, in the purest state in which we are able to procure it, seems to have been first examined by Berthollet,' and afterwards by Fourcroy, but the most elaborate analysis is that of Thenard. He considers it to be essentially acid, and supposes that the acid is the acetic; it contains

1 Journ. de Phys. t. xxviii. p. 275.

2 System, v. ix. p. 280. et seq. He informs us that Vauquelin and he discovered urea and phosphate of lime in the perspiration of horses, p. 289.

an appreciable quantity of muriate of soda, and perhaps of potash, with traces of the earthy phosphates, and of oxide of iron; there also appears to be a very minute quantity of an animal matter." The matter of perspiration has been still more recently examined by Berzelius, and with results considerably different from Thenard's. He indeed supposes it to contain a free acid, but this he conceives to be the lactic, accompanied with the lactate of soda, together with the muriates of potash and soda, and a minute quantity of animal matter; it appeared, indeed, to be identical with the substance which Berzelius had announced as existing in the serosity of the blood, and many other of the animal fluids.

It may be reasonably doubted whether the aqueous exhalation from the lungs should be considered as an immediate secretion from the blood. I have already made some remarks upon its origin, and have stated that I conceive it, upon the whole, more probable that it proceeds merely from the aqueous part of the mucus, which is evaporated from the surface of the pulmonary vesicles, than that it is a distinct or separate secretion. So far as its chemical constitution has been examined, it appears to be the same with the cutaneous transpiration, and to consist of water, perhaps, holding in solution minute portions of saline

3 Chimie, t. iii. p. 712.

4 Thomson's Ann. v. ii. p. 415; Med. Chir. Tr. v. iii. p. 256, 7; Ann. Chim. t. lxxxix. p. 20. See also Thomson's Chem. v. iv. p. 547. et seq..; Henry's Elem. v. ii. p. 434; Ure's Dict. Art. "Sweat."

or animal matter, but we have no very certain information respecting either their quantity or exact nature.5

The second class of secretions, the albuminous, constitute a very numerous and important series of substances, some of which are in the solid, and others in the fluid form. All the membranous, or white parts of animals, as they have been termed, consist essentially of albumen, which appears, from the experiments of Mr. Hatchett, to differ from the albumen of the blood only in being detached from the greatest part of the extraneous matter with which it was united, and in being in a coagulated state. We have also a considerable number of fluid albuminous secretions; the surfaces of all the close cavities of the body, such as the thorax, the abdomen, the pericardium, the ventricles of the brain, and even the interstices of the cellular substance, are continually secreting a fluid, which seems to differ from the serum of the blood principally in containing a much smaller quantity of albumen. There are many morbid conditions of the body, in which these fluids become præternaturally increased in quantity, sometimes to a great extent, so that we have an oppor

5 We are informed by M. Magendie, in his Mem. on Transpiration, that M. Chaussier has proved that the vapour from the lungs contains a quantity of animal matter, by keeping a portion of it in a close vessel exposed to an elevated temperature; upon opening the vessel a very evident putrid odour was exhaled from it; p. 16.

Phil. Trans. for 1800, p. 399. et alibi. See vol. i. of this treatise, p. 43. et seq.

tunity of examining them with great accuracy. Many chemists, both on the continent, and in this country, have applied themselves to this investigation, and it is clearly ascertained, that they consist of a certain quantity of albumen, which may be regarded as what gives them their essential character, of another animal matter similar to that found in the serosity of the blood, and of the same neutral and earthy salts which we find in that fluid. It would appear that the salts and the additional animal matter are nearly in the same proportion in all cases, while the proportion of the albumen is varied from a quantity nearly equal to that in the serum of the blood, to one almost too small to be recognized even by the most delicate tests. This, therefore, affords an instance of that inconsistency, to which all attempts at arrangement are liable, where we place a secretion in the class of albuminous, although the smallest quantity only of albumen enters into its composition.

The morbid albuminous fluids, which we have the most frequent opportunities of examining, are those from the abdomen, from the ventricles of the brain, from the pericardium, from the cavity of the spine, from that of the testicle, and from the cellular texture generally. As a general rule, the fluid from

7 Berzelius, Ann. Phil. v. ii. p. 384, 5, and Med. Chir. Tr. v. iii. p. 251. et seq.; Henry's Elem. v. ii. p. 431, 2; Thomson, Chem. v. iv. p. 528; Thenard, Traité, t. iii. p. 683, 4. p. 686, 7; Magendie, Physiol. t. ii. p. 344..6.

8 Marcet, in Med. Chir. Tr. v. ii. p. 340. et seq.; Bostock, in ditto, v. iv. p. 53. et seq.

the cavity of the abdomen contains the greatest: proportion of albumen, and that from the brain, the least, but there are many exceptions to it. We also find that the fluid from the same part contains more or less of the animal matter according to the states of the constitution, the rapidity with which the deposition of matter is made, the length of time in which the fluid has remained in the cavity, and probably from other circumstances; but I do not find that we are able to lay down any general principles which are applicable in all cases. By comparing together a considerable number of experiments, which I have performed at different times on fluids of this description, I have been led to conceive, that the variation in the quantity of the albumen is much greater than of the other ingredients, so that while in certain of these fluids, as for example, in that of hydrocephalus, it is not more than one-third or one

9 In a very remarkable case of chronic hydrocephalus, which occurred lately in Guy's Hospital, the fluid was not only in extraordinary quantity, but contained an unusually large proportion of solid contents. I examined a portion of it, with which I was favoured by Mr. Aston Key, and found the proportion, both of the animal and of the saline ingredients, to be very much more than is usually present in fluids of this description, so as to be nearly double the average quantity. How far this peculiarity belongs generally to the disease in its chronic form, is a question which, I believe, the present state of our knowledge does not enable us to answer. It is much to be desired, that the particulars of so very curious a case may be given to the public, by some of the gentlemen who assisted in the. examination,