GLAND. 



iliey contain fome fJine and oily matters. Many of our 

 fluiJs bc-lon^ to this divilion. Some are expelled from the 

 }jody, and are ordinarily deemed cxcrementitioua ; luch are 

 the urine, which is not coagulable in the natural Hate ; the 

 infenfible Sandorian perfpiration, and the puhnonary exha- 

 lation. Sweat is a mixed fluid, containing oily or febaceous 

 matter, together %vith water. Several of the fluids, which 

 are delHned to ferve particular purpofes in the animal econo- 

 my, contain very little except water. This is the cafe witli 

 t.he focretion of the proper falivary glands, with that of the 

 pancreas and lacrymal gland; with the perfedly pure and 

 tranfparent aqueous humour of the eye, and other watery 

 fluids in the fame organ. 



2. Mucous fluids. Thefe differ from water in being lefs 

 fluid ; they are tenacious, fo as to adiiere to folid bodies, 

 and ropy. They mix with water, are inllpid and inodorous, 

 and nearly colourlefs. The evaporation of their aqueous 

 parts reduces them into hard and dry crufts. AA;ids do not 

 coagulate them; but alcohol has a flight effecl. They yield, 

 on dilUIlation, a large quantity of water, volatile fait, oil, 

 and a carbonaceous refidue. To this divifion belong the lu- 

 bricating fluids, which are poured out over the extenfive 

 furfaces of the refpiratory, digettive, urinary, and genital 

 organs, and all the parts aoiincfted with them. 



3. Gelatinous fluids; which are coagulaMc- by heat, warm 

 water, alcohol, and acids, remain fluid below 148' Fahren- 

 kcit ; and have a mild or flightly fahne tafte. Haller places 

 in this order the ferum of the blood, the lymph con\eyed by 

 the abforbents, the water of the amnios, the ferous exhala- 

 tions of the circumfcribed cavities, the lymph of the cellular 

 fubllance, and the fluid of the Graafian ovula. He alfo 

 places in this divifion the fynovia of the joints, and the fluid 

 of the tendinous theca-; obferving, at tlie fame time, tiiat 

 thefe are partly compofed of oily matters. 



4. Oily fluids. Thefe are reprefented by Haller as more 

 perfectly animalized produftions : they are freed from the 

 fupcrfluous quantity of water, and are inflammable; or at 

 leafl: contain much of that matter which takes fire and defla- 

 grates. At their firfl; produftion they contain much water, 

 fo as not to be capable of inflammation, nor to poflefs their 

 peculiar charafters, but rather to refemble mucus or gela- 

 tine: they undergo changes afterwards, which deprive them 

 cf their aqueous parts, and render them more vifcid and 

 oilv. The fat and the medullary fubllance of the bones, 

 are the mod extenfive fpccimcns of this order: it contains 

 alfo febaceous matters of various kinds, as the greafy cuta- 

 neous matter, the Meibomian fecretion of the eye-lids, that 

 cf the glans penis, and of the external organs in the female. 

 The bile, cruor of the blood, milk, and proftatic' fluid, be- 

 long to the fame clafs. 



Such are the four divifions, in which Haller has. arranged 

 the animal fluids : he obferves that feveral, being of a mixed 

 nature, do not belong exclufively to either clafs, but ought, 

 from the diverfity of their principles, to be referred to more 

 than one: indeed there is hardly any, which can be rigo- 

 rouflv faid to confifl of a fingle clement. Then, again, many 

 evid/mly contain more fluids than one, formed feparately in 

 the lirfl inllance, each in its appropriate organ, and after- 

 wards mixed together. Thus the femen contains the fecre- 

 ticns of the teftis, proflate, andveflculx; the fweat is made 

 lip of the water of perfpiration with the cutaneous oil; the 

 tears are a mixture of water, mucus, and febaceous matter; 

 fpittle contains water and mucus, &c. 



The vaft improvements in the fcience of chemiftry fince 

 'the time of Haller mull neceffarily have fubvcrted the bafis 

 fif the arrangement jull defcribed ; which, when coiifidered 



by a chemift of the prefent day, would be found open t* 

 objeftion at all points. The deficiencies of the claflification 

 are too obvious to render it neceflary that we fliould parti- 

 cularize them. 



Blumcnbach has clafled the produdls of fecretion on s 

 fomewhat different principle. " The fecreted fluids," fay* 

 he, " difplay on one hand fo much variety, while on the 

 other they feem to be joined by fo many points of affinity, 

 that their arrangement in clafles mull be in great meafure 

 arbitrary. They may, however, be difpofed in the following 

 order, according to the flighter or more efl(.'ntial changes 

 and modifications which their elements, contained in the 

 mafa ot the blood, undergo in the fecretory organs. Milk 

 may be placed in the firfl: rank, as coniifting apparently 

 of a very fimple modification of chyle, and formed from 

 the blood by a very eafy procefs after the influx of the 

 chyle. The watery fecretions come next, fo called from 

 their fluidity and tranfparency, although they differ ma- 

 terially from water in the nature of their conftituent elements, 

 particularly in containing a portion of albuminous coagu- 

 lable matter — including tlie fluids of the eye; the tears, tlie 

 matter of perfpiration, the exhalations in tlie cellular fiib- 

 ftance, and in tlie thoracic and abdominal cavities, to which 

 the liquor pericardii and tlie fluid of the ventricles feem to 

 be analogous. The urine, ordinarily referred to the aqueous 

 fluids, is diftinguiflied by very remarkable peculiarities. The 

 falivary fluids, concerned in the funftions of maltication, 

 digeilion, and chylification, feem to he rather more changed. 

 Then follow the mucous fecretions, fpread over the fur- 

 faces ef moll of the vifcera belonging to the natural and 

 generative funftions, as well as tlie cavities of the nofe, 

 larynx, and relpiratory organs. The mucus in the interior 

 of the eye, as well as that under the epidermis, do not ap- 

 pear to differ eflentially from the preceding. Under the 

 title of adipous fluids may be clafled, befides the common 

 fat, the medulla of the bones, and the febaceous matter 

 of the fl<in (including alfo the cerumen of the ears). The 

 greafy matter formed under the prepuce about the corona 

 glandis of the mple, and the fimilar production in the fc. 

 male pudenda, may be referred to the fame clafs ; as well 

 as the fecretion of the Meibomian palpebral glands. The 

 liquor of the amnios, and the fynovial fluids, are commonly- 

 deemed gelatinous ; but their real nature is not yet under, 

 ftood, neither is that of the fluid, hitherto unnamed, 

 thrown out in the uterus under the venereal llimulus, known. 

 The fluid contained in the early months of conception 

 between the chorion and amnios, that of the veficula umbi- 

 licalis, and that which furrounds the veflels of the umbilical - 

 chord, is as yet little underllood. The contents of the 

 Graafian veficles, and the prollatic fluid, feem to be truly 

 ferous or albuminous. The male femen is quite a peculiar 

 produd, not to be compared to, or clafled with, any other : 

 and the fame remark will hold good alfo of tljc bile." Iii- 

 ftitut. Phyfiolog. fed. 32. 



The divifion of this able phyfiologifl would be natural 

 and inllrudlive, if the animal fluids deviated from the nature 

 of chyle by gradations wliich could be eafily perceived and ■ 

 marked. But we really cannot eftablifli among tiiem any order 

 correfponding to their natural compofition ; and t'he dif- 

 ferences obfervable between chyle and fat, between the 

 aqueous fluids and bile, conftitute intervals, wliich we can- 

 not appreciate or meafure. Indeed there are often fo many 

 differences and fo few relations between one fluid and an- 

 other, that we can fcarcely compare them at all. 



The vaft progrcfs uhich chemiftry h;is made of late 

 years, and the vahiable difcoveries \sith which the analytis 



uf 



