But the connection of the excretory duct and the Weberian organ is limited to the hare and lagomys. In all the other Mammalia the two structures open near to each other without any communication. Now if in spite of this, the Weberian organ has the function of a seminal receptacle, this can only happen by the sperm, which has been previously poured into the urethra, being discharged through the lower aperture of the Weberian organ into its interior.
\le will not quite deny the possibility of such an occurrence; but the probability of it seems but small. At any rate a contraction of the muscular layer around the urethra would be necessary thereto; but, without offer ing any new hypothesis, it would scarcely be possible to perceive why the sperm should thus be sent Upwards rather than downwards. The verumontanum alone would not be able to prevent this.
Such considerations would be silenced by direct observation ; but hitherto no one has ever met with real semen in the Weberian organ, except in the hare. Morgagni states, that on pressing the human vesiculm seminales, he has seen sperm exude from the prostatic utricle. But the correctness of this state ment is rendered very doubtful by the fact, that the examination was made at a time when the accurate diagnosis of semen was not yet understood. A fluid may certainly have exuded from the Webe-ian organ, but that it was sperm is very doubtful. It might easily form the contents of the Weberian organ, where, as is sometimes the case, this has an abnormal communication with one or the other vas deferens.
I will not bring forward further arguments against the import of the Weberian organ as a seminal vesicle, such as its little capacity in many instances, &c. They would only prove that such a function is sometimes impossible.
A third theory of the function of the vesi cula prostatica has been lately suggested by Weber. According to this view it is a kind of valvular ventricle, by which the urine is hindered from penetrating the vasa defe: rentia. In order to this, the urine must, like the semen in the previous view, enter into the vesicle, which, distended by it, must by its own pressure close the ejaculatory canals. Hence the same difficulties recur as in the first case. Since the urethra contains urine only during the act of micturition, sad is at other times empty and collapsed, this fluid must, even in its passage through the tube by which it is discharged, pass into the vesi cula : a fact which is the less supposable, inasmuch as to this end a backward move ment of the urine would be necessary. Be sides in many cases the situation of the Weberian organ is such that, even if distended by a fluid, it could not possibly operate in such a way. And moreover, even where it might perhaps be possible, it seems unneces sary, since' the tumid or papillary margins of the orifices of the vasa deferentia are suf ficiently closed by the passage of the urine itself.
One other conjecture of the physiologi cal value of the Weberian organ still remains to us,— viz. that it is a secretory appa ratus. It was found by the older anatomists that here and there, for instance in the horse, it was filled with a thick fluid, mostly of a yellow tint. As was previously remarked, this can only be secreted by the coats of the Weberian organ. Morgagni mentioned that the inner clothing of the organ was a mucous membrane, and possessed a glandular texture ; • and the later researches of Huschke and Leydig have succeeded in verifyino. a number of small glands therein. These glandules have a different form in the different animals ; for instance, in the rabbit they are simply spherical ; in the boar they are elongated tubes provided with buds and processes.
Whether such glandules always exist in the Weberian organ must be verified by further careful researches. Leydig could not find them in the dolphin, nor could I in the dog. At any rate they are absent where, as in the deer, &c., the cavity has disappeared.
Exteriorly to this mucous membrane, which possesses a layer of cylindrical cells as an epithelium, there is a layer of smooth mus cular fibres, which take the longitudinal di rection. In the hare only, in whom they form a considerable layer, especially at the lower end, they are more twisted together. It is evident that this latter arrangement is connected with the import of their Weberian organ as a seminal vesicle. At all events they are thus susceptible of more powerful contractions, which one may produce in the recently dead animal by galvanic and other stimuli for a considerable time. Together with these muscular fibres there is a quantity of areolar tissue with white and yellow fibres. This sometimes predominates, and where the cavity disappears, it seems to occur alone.
It can no longer be doubted that the Weberian organ, at least where it is com pletely developed, and possesses an internal cavity and an opening, may prepare a secre tion ; but the nature and physiological import of the secretion are as yet unknown to us. II. Meckel* states, that he once found a clear vitreous mass in the Wcberian organ of the rabbit, which from its re-actions was gelatine. Nevertheless it is very improbable that the secretion always consists of this sub stance, at least if I can judge from its external physical properties.
This secretion may easily be carried away from time to time with the urine or the sperm. Whether it plays any further part — whether it is possibly, like the secretion of the prostate, subservient to the dilution of the semen (as may be conjectured from the arrangement of the Weberian organ in the hare) or to other purposes, we know not. After all, however, the function of the secretion can scarcely be an important one.