There are a few cases of intense jaundice which terminate in coma and death as rapidly as the ischuria renalis does, and with as little morbid appearance in the brain to explain this kind of fatal termination ; and in several such cases the remarkable phenomenon has been observed after death, that the bile-ducts have been pervious and empty.* It is obvious, that it is this last circumstance only, that tan make a case of jaundice analogous to cases of the ischuria renalis. If it shall appear to be a general fact, that the cases of jaundice presenting this remarkable appearance on dissection are those which terminate with unusual rapidity in the way of coma, the analogy will appear to be complete ; and when such cases are compared with those, much more frequently occurring, where the excretion of bile is only obstructed, not suppressed, and where months frequently elapse without any bad symptom occurring,—it appears a reason able conjecture, that the retention in the blood of matters destined for excretion, is more rapidly and certainly injurious than the re absorption of matters which have been excreted from the blood at their ordinary outlet, but not expelled from the body.
Although there is still much obscurity in regard to the intention of the menstrual dis charge, yet it may be stated as a general fact, that the suppression of this evacuation is more frequently followed by injurious effects (particu larly affections of the nervous system, or vica rious haemorrhage) than the stopping of an equal amount of hwmorrhage, going on equally slowly, would be; so that the general principle applicable to other excretions is exemplified here likewise.
IV. The next question in regard to the ex cretions is, in what manner they are effected ; and on this question, although we must profess ignorance in the last result, yet it is instructive to observe, what seems now to be well ascer tained, that the large size, and apparently com plex structure, of several of the organs of excre tion, appear to be no part of the contrivance for the formation of these fluids from the blood.
It is stated by Cuvier, as the result of a general review of the structure of glandular organs in different classes of animals, that pro ducts very nearly resembling each other, and evidently answering the same ends, are formed in organs where the structure, and the disposi tion of vessels are very various ; and again, that substances the most widely different are formed in organs that are in these respects ex tremely similar ;I- and that this should be the case will not appear surprising when we consider the result of the most minute and accurate observations on the ultimate structure even of those secreting organs, which form substances the most dissimilar to the general nourishing fluid, either of animals or vegetables. " Chaque cellule de Is structure vegetale," says De Candolle, " pent etre consider& comme une vesicule organique et vivante, qui est entoune, ou de cavitCs dans lesquelles abordent des liquides, ou de cellulesremplies elles-memes de liquides. Cette vesieule, par sa vitalite propre, absorbe une partie du fluide qui l'entoure; cc fluide est ou de l'eau prsqiie pure, et alors elk en est simplement impregnee et lubrifiee ; on de l'eau plus ou moins chargee de cette maare gommeuse, elaboree dans les feuilles, et d'autres mares alimentaires qui peuvent se trouver portees avec In seve dans les diverses parties. La vesicuk qui l'a absorbiv liii fait
subir tine action deternthae d'apris sa propre nature, et cette action modifie les materiaux contenus dans la cellule, de manibre it en fake, ou l'une des matieres communes que nous avons considerees, ou l'une des inatkres quo nous aurons bieuttit t examiner, telles que les !tulles volatiles, les resines, tke. Certains vaisseaux analogues A Ia nature des cellule jouent le mime role sous cc rapport. Les matieres ainsi loealement elaborees pcuvent, ou rester dans les eellules ou les vaisseaux qui leur out donne naissance, ou s'extravaser au dehors et donner lieu, soit A des excretions, soit A des transports des males d'une partie ii I'autre du tissu." The description given by Dutrochet of the act of secretion as it may almost be detected in the glands of the lower classes of animals, is exactly similar. " Entre les vesicules qui composent le tissu organique des animaux ram pen t les vaisseaux sanguins, chez les animaux it circulation : ees vesieules sont appliquees sur les parois des vaisseaux; et it est certain que Ia cavite des vesicules ne communique point immediatement avec la cavite. des vais scans puisque le mime fluide n'existe point dans leurs cavites. Ce fait cst facile It verifier, en examinant au microscope le tissu d'un organe secretive chez uu mollusque gas teropode, celui de la foie par example : on volt toutes les vesicules de cet organe remplics par la bile, que l'on distingue sa couleur, tandisque fcs vaisseaux sanguins qui cotoient ecs vesieules n'ont que la diaphaniete que leur donne l'etat ineolore du sang qui les remplit. Ainsi, les vaisseaux sanguins n'existent que comme des moyens d'irrigation pour les vesi cules qu'ils cotoient, et ce n'est peut-etre que par filtration que le 'Wide sanguin peatre, en si modifiant, jusque dans ces vesicules elemen taires. Le systeme sanguin, considers dans son entier, forme une cavite sans issue, dans laquelle rien ne peut entrer, et de laquelle rien ne peut sortir, autrement que par filtration."-f Any one who is acquainted with the elabo rate Vasorum Lymphaticorum Ilistoria" of Mascagni, will recognize the perfect accordauce of this statement with the result of his careful and minute investigation of the structure of the secreting organs in the higher animals.! NVe may consider, then, the act of secretion, " en demiere analyse," as consisting simply in the passage of certain portions of a compound fluid through a thin living membrane, and the exclusion of others; or, according to the for tunate expression of Dutrochet, as a chemical filtration. " All that is necessary for any kind of secretion in a living animal," says Mr. Mayo, " is a vascular membrane, and all the arrangements of the glands appear to be merely contrivances for conveniently packing a great extent of such a surface in a small compass." And if we are asked, to what cause we can ascribe this escape of certain matters from the circulating fluid through one portion of mem brane, and of others through another, we can only answer, in the words of this last author, that it depends on the exercise of certain "vital affinities," peculiar to the living state, and the existence of which will always be an ultimate fact in Physiology, although we may attain to a knowledge of the laws according to which they operate.