e L A N D. 



cks in tlie bony fyftcir. Hct.cc vccretion aUvay"> implies 

 forae chnuge or moclilication i:i the matlor v.Iiich rciults 

 from its cxercilV. Comioifl". Cliiiii. fcdi. 8. ord. 4. 

 art. 5. 



Another notio:i, as dcilitutc of all folid foundnticn as the 

 f;>v:;icj-, is, that tiic blood undergoes certain Vhunfres as it 

 arri<-cs at the ghndj ; that it afruini-s a pecidiar ccnipcfition 

 before it penetrates the organ. It has been afi'erted l!>at 

 tlie bbod-veflels are l"o arranged as to produce partie\dar mo- 

 difications in the contained fluid, and that this is a difpolition 

 preparatory to the iinal procefs. The hepatic fccretion has 

 been conlidercd to afford the clearell example of fuch pre- 

 vious clnnges. The ftrudlurc and nunihcr of the veffels 

 which furround and enter the organ, the j)r(iportion of ti'ofe 

 which carry blood or white fluids, tliedid'erent tiinperatures 

 fuppofed to depend on the'e pi-oportioiis, in a word, all 

 thofe points of organization which can pcilibly influence the 

 nature of the blood, are faid to be fufficlcntly diverlilied in 

 order to produce in tlie chemical properties of the fluids a 

 difpofition favourable to the formation of faliva in the neigh- 

 bourhood of tie faUvary glands, of urine in that of the 

 kidney, 5:c. This diipofition, depending on the vafcular 

 apparatus, has been reprefented to confiit particularly in 

 a retardation, acceleration, cooling or warming of the 

 blood, or in the lofs, by abforption, of fome ol its prin- 

 ciples. But what fenfible canfe can produce thcfe cfiects ? 

 Does not the blood flow through the trunks which are 

 going to the glands ju!l as in other veflels ? In fliort, what 

 is tlie change ? The fuppotition in quefllun is a complete 

 aflumption ; not fupported by a Angle faft, and contrary 

 to obfervation as tar as our knowledge hitherto extends. 

 For we can deteA no difference in the blood drawn from 

 the carotid, fpcrmatie, hepatic or renal arteries. We 

 ■have been furprifed to find this opinion adopted and fup- 

 ported by Fourcroy ; but the whole of his remarks on the 

 fubjecl in the " Sylleme des Connoiflances Chimiques," 

 feci. 8. ord 4. art. 5. do not contain a fingle proof, and afford 

 an example of vague and completely illogical llatements. 

 We do not mean to deny that there maybe particular con- 

 ditions of the whole mais of blood favourable to certain fe- 

 cretions. Thu.-;, after drinking copioufly of watery fluids, 

 we find a much larger portion of urine fecreted ; and the 

 cutaneous exhalation is often augmented from the fame 

 caufe. 



In our endeavours to difeover the mechanifm of fecretion, 

 it will be belt for us to feletl the moll fimple mode of this 

 fundlioa. Now the exhalation from ferous membranes, and 

 the mucous fluid covering the furface of many cavities in 

 the body, are examples of this kind. We can difeover no- 

 thing in tliele organs but vafcular ramifications united by 

 cellular lubllance. Injerted fluids in the djad body follow 

 the fame route whicli the fecreted liquors follow in the living 

 ftate. And the fame oblervation m.ay be applied alfo to 

 the cafe of fecretions in fome of the more compkx inllances. 

 ♦^ Water,' ' fays Haller, " tinged with colouring matter, 

 ifmglafs, or oil of turpentine, thrown into the arteries of a 

 young fubjeft, and occafionally even fuet, in the experi- 

 ments of Ruyfch and Albinus, have exuded in numerous 

 fmall drops Irom the ikin, after the removal of the cuticle 

 in warm water, io as to imitate very clofely the proceedings 

 of nature. I have alio repeatedly leen water, coh)ured with 

 blue, and injeded into the lungs through the inferior cava, 

 run out witli much froth from the trachea. In the kidney, 

 water, air, or luet will pafs through excretory tubes continu- 

 ous w.Ui the arteries into the iijfundibula and pelvis. Oil 

 of lurpentine and quickfilver have pafled inio the cham- 

 ber of the aqucotis humour from the arteries : in 



ttic fame way inicfted water imitates the eourfe of the 

 tears, and exudes abundantly from the whole intern;;! fur- 

 face of the eye-lids." Elcm. Phyfioi.t. 2. p. 374. Phy- 

 fiolo'nlts have indulged in confidcrable difputes concerning 

 this kind of fecretions. " Sor.ie," fays Blumenbach, "affert 

 that all feparalion of fluids from the read's of blood is ac- 

 complifiied merely by pores in the blood-vefftls, and thofe, 

 as they fay, of an inorganio nature ; while others deny 

 altogether the cxidencc of fccretory pores. I fufpcdt that 

 this difference of opinion n-.uil be reiolved into a verbal dif- 

 pute. On the one hand, I muff confefs, unequivocally, that 

 I know not what notion to form of inorganic pores in an 

 organized body, fince all the openings in fuch bodies mull 

 belong to their organic nature, and he regulated by their 

 vital properties. On the other fide I do not conceive thai 

 the orifices or pores in the coats of the veflels, the cxiflencc 

 of vhich cannot be doubted, differ efli:ntially, in regard to 

 their functions, from the cylir.drical duds, in which fccx-ctivin 

 is perfL-rnicd in the conglomerate glands, and in the glan- 

 dular viiccra : fince it is probable tlsat th.e icparation oi 

 fluids depends more on the vi<?.l properties than on the forn^s 

 of the fecretory organs.'' Inililut. Phyfiolog. fedl. 32. 

 § 469, note I. 



However iimple the procefs of fecretion may be deemed 

 in the cafe juil fpecified, and however clofely the pro- 

 ceedings of nature may be imitated by the experiments with 

 injeftions, we fliall ftill find ourfelves entirely ignorant ot 

 the eirential circuniltances of th.e procefs ; i. e. we cannot 

 e.splain the formation of the new produft from the blood, 

 and the formation of fuch totally different new combi- 

 nations in organs v.-here no difference of ilruAure can b« 

 detetled. 



Thofe, who wifli to fee the various attempts at explaining 

 the mechanilm of fecretion, may find ample gratification in 

 the third fctlion of the fcventh book of Haller' s great work : 

 where he gives his ufual detail of all that has been written 

 on the fubjeft. The reader will be very willing to fparc us 

 the taflt of recounting all thefe dreams, and the itill more 

 difgufling toil of refuting them. We fliall merely mention 

 one opinion, on which phy'.iologifts lay fome ffrefs even in 

 the prefent day- This refers the diflerence of the fecreted 

 matters to the pecuUar arrangements of the minute arteries 

 of the glands. Ruyfch, who excelled in the art of making 

 anatomical preparations, was led to remark, in his emjiloy- 

 ment of injeftions, that the ultimate arterial ramifications 

 differ in the different fccretory organs, and indeed that there 

 are charafteriftic differences in this refpeft in all the ftrudtures 

 of the body. This explanation may poffibfy be true, and 

 we cannot perhaps completely overthrow it : but this is all 

 that we can fay in its behalf. We muff obferve, in the firit 

 place, that a convfc account of the fafts, and an exaft de- 

 fcription of the diflerent valcidar networks, is yet a defidera- 

 tum ; for the quellion concerns the very fmalleft capillaries, 

 from which the tubes conveying the new product commence. 

 Now the larger ramifications, inch, for inltance, as will ad- 

 mit feveral globules, do not differ fufficiently from each 

 other to account for the diverfity of the fluids produced in 

 the various organs. Indeed fimilar veffels often produce the 

 moll oppofite produdls. The ftruflure of tile cortex cere- 

 bri, of the fpleen, and of tlie placenta, is very much alike 

 with the moft diflimilar refults. The veins, too, are arranged 

 like the arterit s, as we fliould conclude, certainly not fop 

 the purpofes oi fecretion. Very different arrangements of 

 bloo<l-veffel3 may be*feen in various membranes which pro- 

 duce the fame kind of exhalation. 



RecoHifc has been had to the fcience of chemiffry , in order 

 to explain the funtlion of fecretion, ^ut no affiilauce has b?e.i 



liitbert* 



