884 



measure, removed from the influence of external causes^ bring forth al- 

 most indiscriminately, at all seasons of the year. To prove still farther^ 

 that is from counteracting, by the resources of his industry* the influence 

 of nature^ that man has succeeded in resisting; the influence of the sea- 

 sons, in the reproduction of his species, 1 may observe, that this effect 

 of temperature is more absolute, the farther the species is from man; 

 hence the spawn of fishes and frogs is productive sooner or later, accor-* 

 ding to the earliness or lateness of the season, and thus a great number 

 of insects depend on the heat of the weather for their powers of repro- 

 duction, and for their existence. 



CCI. Of the organs of generation in man. Aristotle, Galen, and their 

 verbose commentators, have expressed the analogy which subsists be- 

 tween the organs of generation, in the two sexes, by saying that f.hey 

 differ only in their position, being external in man, and internal in woman. 

 There is, in fact, a considerable resemblance between the ovaria and the 

 testicles, the fallopian tubes and the vasa deferentia, the uterus and the 

 vesiculoe seminalis, the vagina, the external organs of generation in wo- 

 men, and the male penis. The former secrete the seminal fluid, and fur- 

 nish in man or in women, a matter essential to generation (ovaria and 

 testicles.) The fallopian tubes, like the vasa deferentia, convey this fluid 

 into recepticies where it has to remain for some time (uterus and vesiculse 

 seminales.) These contractile cavities, which serve as reservoirs to the 

 semen, or its product, part with these substances, when they have re- 

 mained within them a sufficient length of time ; lastly, the vagina and 

 penis serve to expel them. However striking such analogies may be, we 

 are not justified in inferring a perfect resemblance between the organs of 

 generation in the two sexes* Each of them fulfils, in ,the act of repro- 

 duction, functions perfectly distinct, though of reciprocal necessity. 



The prolific fluid is secreted by the testicles : these organs are two in 

 number, covered by several coats, one of -which, covered by the skin, and 

 known under the name of scrotum) resembles a bag containing both these 

 organs : it contracts on the application of cold, is relaxed by heat, and 

 possesses a degree of contractility more evident than the other parts of 

 the cutaneous tissue. The dartos forms a second cellular envelope com- 

 mon to each testicle* The tunica vaginalis, a serous membrane, affords 

 an immediate covering to them, and reflecting itself over the surface, is 

 disposed with regard to them, as the peritoneum with regard to the abdo- 

 minal viscera, that is, it does not contain them within its cavity. Lastly, 

 the testicles are covered by a fibrous, white* thick, and very consistent 

 membrane : it is termed tunica albuginea, from the inner surface of which 

 there arise a considerable number of membranous lamina, which, crossing 

 one another, within its cavity, form cells containing a yellowish vascular 

 substance. This substance contained within the tunica albuginea, has so 

 little consistence, that it would very soon be dissolved, if the testicle were 

 stripped of its outer covering. It is formed by the seminiferous tubes, 

 which are small capillary vessels extremely tortuous and coiled on them- 

 selves, arising, probably, from the extremities of the spermatic arteries, 

 all directed towards the upper part of the oval formed by the testicles, 

 joining in this place, and forming about ten or twelve tubes, which unite 

 into a cord situated within the tunica albuginea* called the corjius High- 

 morianum. The ten or twelve ducts which unite into a fasciculus, and 

 form this cord, pass through the membrane within which they are con- 

 tained, unite into a single canal which is convoluted, and form? a sub- 



