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The immediate cause of oestrum is the existence of fully matured ova within the ovaries of the female; and when these escape, vibram five fingers without coition and consequent impregnation, we observe a temporary cessation of the desire until other ova are equally perfected. It follows, therefore, that impregnation can only be effected when the ova are in this condition. The time occupied in the development of the ova differs in different animals, hence the variation we witness in their return to the male. vibram fivefingers The ordinary symptoms of oestrum in the cow and other animals are too well known to render it necessary to repeat them ; and it is sufficient to state that they denote a highly excited state of the system. Impregnation is produced by the fecundating fluid of the male acting on the matured ovum of the female, which action probably takes place in the ovarium. Physiologists are acquainted with many phenomena which illustrate this. The way in which the male or seminal fluid finds its course through the body and horns of the uterus, and thence through the Fallopian tube to the ovarium, vibram five fingers shoes is disputed. Its conveyance, however, is generally believed to be effected through the agency of moving filaments, called spermatozoa, with which it abounds. Hence it is all important that the Fallopian tubes should be pervious, or impregnation cannot take place. If their passage be obliterated, as we have often proved by the experiment of passing a ligature around them, the animal is as effectually rendered non-productive as if the whole parts had been vibram five fingers sale taken away. The above facts explain how it is that, in the ordinary operation of spaying, the simple removal of the ovaries, leaving in situ the uterus with its horns and Fallopian tubes, destroys the desire as well as the power of conception, and when by accident or otherwise the operator leaves behind an ovarium, all other parts being cut away, the animal five fingers shoes returns to the male, notwithstanding she is sterile.The impregnated ovum when it bursts and escapes from its ova-sac is seized or entangled by the fimbriated edge of the Mbt shoes clearance sale Fallopian tube, and subsequently conducted into the uterus, where it excites that extraordinary action which leads to the formation of a new creature in every essential particular like its parent. Should the ovum not be caught by the fimbria, it falls into the cavity of the abdomen, but is not necessarily destroyed, as even here, although out of its proper matrix, it sets up an analogous action to that which otherwise would have been produced within the uterus.