many cases, more than twice as rapid when the mucus had been removed as when still adherent.

a. Secretion of the Peyerian Glands.

The morphology and functions of the Peyerian follicles or glands have been investigated elsewhere. They are peculiar in having no outlets; the fluid elaborated by them from the blood being poured, by the bursting of the formative cells, on the mucous surface of the intestinal canal.

b. Secretion of the Ovaria.

In many respects the secretion of the ovaria-the formation of ova. -is accomplished like that of the Peyerian glands. Like them, the follicles of De Graaf are devoid of outlet; and the secretion has to make its way to the surface of the ovary and be discharged,-the Fallopian tube receiving it, and acting as an excretory duct. The mode in which this is accomplished will fall more appropriately under consideration, when the functions of Reproduction are investigated.

2. Follicular Secretion of the Skin.

This is the sebaceous and micaceous humour, observed in the skin of the cranium, and in that of the pavilion of the ear. It is, also, the humour, which occasionally presents the appearance of small worms beneath the skin of the face, when it is forced through the external aperture of the follicle; and when

24.2; carbonate of lime, 21; phosphate of lime 20.0; carbonate of magnesia, 1.6; acetate of soda, and chloride of sodium, traces.

The cutaneous or miliary follicles or glands were refer

1 Vol. i. p. 532.

Sebaceous or Oil Glands and Ceruminous Glands.

1. Section of skin, magnified three diameters. 2, 2. Hairs. 3, 3. Superficial sebaceous glands. 1, 1. Larger and deeper-seated glands by which the cerumen appears to be secreted. 3. A ceruminous gland more largely magnified, formed of convoluted tube 1, forming excretory duct 2. 3. A small vessel, and its branches. 2. A hair from meatus auditorius, perforating epidermis at 3, and at 4, contained within its double follicle, 5,5, 1, 1. Sebaceous follicles of hair with their excretory ducts. (Wag

ner.)

2 V. Bruns, Lehrbuch der Physiologie des Menschen, s. 353, Braunschweig, 1841.

red to in describing the anatomy of the common integument. At times, they are simple crypts, formed merely by an inversion of the common inte

Fig. 327.

gument; at others, more complicated but still a like inversion; and they commonly open into channels by which the hairs issue. (Figs. 44 and 326, 2.)

In certain parts of the skin, they

are more numer

ous than in others. Mr. Rainey-as hereafter remarked-was unable to detect them in the palms of the hands and soles of the feet. Their appearance in the axilla of the negro has been described by Professor Horner. Their granular or composite character in the axilla, he thinks, is sufficiently evident; but the point is yet to be settled, whether their excretory ducts have the tortuous arrangement of those of the ceruminous glands, or whether they be branched and racemose, like those of the salivary. Mr. Hassall affirms, that they are similar in organization to the sudoriparous glands, but much larger.

Cutaneous Follicles or Glands of the Axilla, magnified
one-third. (Horner.)

The secretion from the different cutaneous follicles differs, probably, according to the different character and arrangement of animal membrane from which the cells that form it are developed. There is, certainly, a marked difference between the fluids secreted in the axilla, groin, prepuce, feet, &c., each appearing to have its characteristic odour; although a part of this may be owing to changes occurring in the matter of secretion by retention in parts to which the free access of air is prevented. The cutaneous or miliary glands, depicted by Dr. Horner, are considered by him to be the glandulæ odoriferæ of the axilla. In many animals odorous secretions of a similar character are formed by special organs; but whether the scent peculiar to animals and to races is thus secreted is canvassed elsewhere, and must be regarded as somewhat unsettled.

The cerumen is, likewise, a follicular secretion, as well as the whitish,

1 Vol. i. p. 126. 2 Page 292.

3 American Journal of the Medical Sciences, for January, 1846, p. 13. 4 The Microscopic Anatomy of the Human Body, Part xiii. p. 426, Lond., 1848.

5 P. 294.

odorous and fatty matter-smegma-which forms under the prepuce of the male, and in the external parts of the female, where cleanliness is disregarded. The humour of Meibomius is also follicular, as well as that of the caruncula lachryma

lis of the crypts around the base of the nipple, &c.

The use of these secretions is to favour the functions of the parts over which they are distributed. That which is secreted from the skin is spread over the epidermis, hair, &c., giving suppleness and elasticity to the parts; rendering the surface smooth and polished, and thus obviating the evils of abrasion that might otherwise arise. It is also conceived, that its unctuous nature may render the parts less permeable to humidity.

Fig. 328.

Entozoa from the Sebaceous Follicles.

In the ducts of the sebaceous of one of the sebaceous follicles of the scalp. b. Short follicles, a parasite was dis- variety. c. Long variety.

a. Two seen in their ordinary position in the orifice

covered by M. Simon, of Ber

lin; which has been minutely described by Mr. Erasmus Wilson,2 Professor Vogel, Messrs. Todd and Bowman, and Professor Owen. It is the Acarus folliculorum of Simon, Demodex folliculorum of Owen, and Steatozoon folliculorum of Mr. Wilson. By him two chief varieties of the adult animal are depicted. These are mainly distinguished by their length-the one measuring from the 6th to the 'th, the other from the 6th to the 18th of an inch.

The marginal figure represents them as found by Messrs. Todd and Bowman in a sebaceous follicle of the scalp. They do not appear to be of any physiological or pathological importance.

III. GLANDULAR SECRETIONS.

The glandular secretions are seven in number; the transpiration, tears, saliva, pancreatic juice, bile, urine, sperm, and milk.

1. The Transpiratory Secretion.

A transparent fluid is constantly exhaled from the skin, which is generally invisible in consequence of its being converted into vapour as soon as it reaches the surface; but, at other times, owing to augmenta

'Müller's Archiv., s. 218, 1842.

2 On Diseases of the Skin, 2d Amer. edit., p. 424, Philad., 1847; and in Philosophical Transactions for 1844.

3 The Pathological Anatomy of the Human Body; translated by Dr. Day, p. 453, Lond., 1847.

The Physiological Anatomy and Physiology of Man, p. 425, Lond., 1845.

5 Lectures on the Comparative Anatomy and Physiology of the Invertebrate Animals, p. 251, Lond., 1843.

2

tion of the secretion, or to the air being loaded with humidity, it is apparent on the surface of the body. When invisible, it is called insensible transpiration or perspiration; when perceptible, sweat. In the state of health, according to M. Thénard,' this fluid reddens litmus paper; yet the taste is rather saline-resembling that of common salt -than acid. Wagner, indeed, affirms that it generally shows alkaline reaction; and, at other times, does not affect vegetable blues; but the sweat of many parts of the body,-the armpits for example,-is said always to react like an alkali. Allusion has already been made to the views of M. Donné,3 who considers, that the external, and the internal alkaline membranes of the human body represent the two poles of a pile, the electrical effects of which are appreciable by the galvano

meter.

The smell of the perspiration is peculiar, and when concentrated, and especially when subjected to distillation, becomes almost insupportable. The fluid is composed, according to M. Thénard, of much water, a small quantity of acetic acid, chloride of sodium, and perhaps of potassium, a very little earthy phosphate, a trace of oxide of iron, and an inappreciable quantity of animal matter. Berzelius regards it as water holding in solution chlorides of potassium and sodium, lactic acid, lactate of soda, and a little animal matter; Anselmino,' as consisting of a solution of osmazome, chlorides of sodium and calcium, acetic acid, and an alkaline acetate, salivary matter, sulphates of soda and potassa, and calcareous salts, with mucus, albumen, sebaceous humour, and gelatin in variable proportions; and M. Raspail looks upon it as an acid product of the disorganization of the skin. The solid constituents, according to Simon,' are a mixture of salts and extractive matters, of which the latter preponderate: the principal ingredient of the salts is chloride of sodium. From what he admits to be superficial and merely qualitative investigations, he considers he has established the existence in normal sweat, of-First. Substances soluble in ether; traces of fat, sometimes including butyric acid. Secondly. Substances soluble in alcohol; alcohol extract; free lactic or acetic acid; chloride of sodium; lactates and acetates of potassa and soda; lactate or chlorohydrate of ammonia. Thirdly. Substances soluble in water; water-extract; phosphate of lime, and occasionally an alkaline sulphate; and, fourthly. Substances insoluble in water; desquamated epithelium; and-after the removal of the free lactic acid by alcohol -phosphate of lime with a little peroxide of iron. In the solid matter urea was detected by Landerer."

After evaporation upon a clean glass plate, fragments of epidermic cells are generally observed in it, and crystals are left behind, which

1 Traité de Chimie, tom. iii.

2 Elements of Physiology, by R. Willis, § 204, Lond., 1842.

3 Journal Hebdomad., Février, 1834.

4 Medico-Chir. Trans., iii. 256.

5 Lepelletier, Physiologie Médicale et Philosophique, ii. 452, Paris, 1832.

6 Chimie Organique, p. 505, Paris, 1832.

7 Animal Chemistry, Sydenham Society edit., ii. 101, Lond., 1846.

8 G. O. Rees, art. Sweat, Cyclopædia of Anatomy and Physiology, pt. xxxvii. p. 844, Lond., October, 1849.

Fig. 329.

are those of its contained salts. With great care to avoid admixture, Krause' collected a small quantity of pure cutaneous perspiration from the palm of the hand, where there are no sebaceous follicles. The fluid yielded, with boiling ether, some small globules of oil and crystals of margarin. It was acid, but after twenty-four hours became alkaline, by the developement of ammonia. In another experiment, he found, that the tissue of the epidermis contains a fatty substance independently of the fatty matter secreted on its surface. In a memoir presented to the Académie Royale des Sciences of Paris, MM. Breschet and Roussel de Vauzème first clearly showed, that there exists in the skin an apparatus for the secretion of the sweat, consisting of a glandular parenchyma, which secretes the liquid, and of ducts, which pour it on the surface of the body. These ducts are arranged spirally, and open very obliquely under the scale of the epidermis. To this apparatus they applied the epithet "diapnogenous:" and called the ducts "sudoriferous or hidrophorous.'

112

Each sudoriparous gland consists of a coil or excretory duct surrounded by blood vessels, and imbedded in fat vesicles. Thence the duct passes in the manner represented in the marginal figure, towards the surface, and opens on the epidermis by an oblique valve-like aperture. The excretory duct is lined by epithelium, which is a prolongation of the epidermis. These glands are numerously distributed: but especially so in the palms of the hand, and soles of the foot. In the former situation they amount, according to Professor Krause,3 to 2736 in every square inch; and in the latter, to 2685. Mr. E. Wilson counted the perspiratory pores on the palm of the hand, and found 3528 in a square inch; and each of these pores being the aperture of a little tube of about a quarter of an inch long, it follows, that in a square inch of skin, on the palm of the hand, there exists a length of tube equal to 882 inches, or 73 feet. To obtain an estimate of the length of tube the perspiratory system of the whole surface of the body, he thinks that 2800 might be taken as a fair average of the number of pores

of

b

d

Vertical Section of the Sole.

a. Cuticle; the deep layers (rete

mucosum) more coloured than the the superficial layers more and

upper, and their particles rounded;

more scaly. b. Papillary structure. c. Cutis. d. Sweat-gland,

lying in a cavity on the deep surglobules of fat. Its duct is seen 40 diameters. (Todd and Bowman.)

face of the skin, and imbedded in

passing to the surface. Magnified

Art. Haut, in Wagner's Handwörterbuch der Physiologie, 7te Lieferung, s. 108. 2 Op. cit., s. 131.

3 Breschet, Nouvelles Recherches sur la Structure de la Peau, Paris, 1835. A Practical Treatise on Healthy Skin, p. 42, Lond., 1845.