The inquiry is not without interest, what influence have these deficiencies and imperfec tions in the vas deferens on the evolution and subsequent condition of the testicle ? In the case of the adult which occurred at St. Bar tholomew's Hospital, the testicle was small, and its structure appeared granular, like the undeveloped testicle of a youth, but as it had not descended into the scrotum, and was com bined with hernia, there may have been other causes impeding its due evolution. In Mr. Hunter's case, the testicles which were in the scrotum were very sound. In the case of the man related by Brugnone, the testicle on the side corresponding to the defective vas de ferens was perfectly sound, and nearly of the same size as the other. So also in Bosscha's case, it is stated, that the testicle was sound. Although either of these defects in the vas deferens renders the gland an useless organ, and if it occurred on both sides of the body, would necessarily cause impotency, these cases, nevertheless, tend to chew that the absence or imperfection of the excretory duct does not prevent the development of the tes ticle at the proper period, and has no direct influence in causing it to waste; and these inferences are fully confirmed by experiments on animals, performed by Sir A. Cooper and by myself.* These cases and experiments show, then, that the testicles may be properly developed, though a physical obstacle to the elimination of their secretion is present from birth ; and that so long as the testicles exist entire, though to no purpose, the individual acquires and preserves all the marks of the male sex ; the secretory organ alone appear ing to be that upon which the sexual charac ters depend. The engorgement of the se minal ducts with sperm is liable, it is true, to cause inflammation of the testicle, which may end in atrophy, but this is only a secondary and occasional effect of the interruption in the excretory duct.
Imperfect transition. — It occasionally hap pens that at birth one or both testicles have not passed into the scrotum, being detained either in the abdomen near the groin, in the inguinal canal, or in the groin, just outside the external ring. In a table of one hundred and three male infants, examined by Wrisberg at the time of birth, it appears that seventy-three had both testicles in the scrotum ; in twenty-one, one or both were in the groin. Of these, five had both, seven the right, and nine the left in the groin ; in twelve, four had both, three the right, five the left, only in the abdomen.t According to this table, the imperfection occurs rather more frequently on the left side than on the right, in the proportion of seven to five. In twenty-five cases examined at different ages, varying from five to sixty,—sixteen of which came under my own observation, the remainder being taken from the recorded experience of others,—in thirteen the imperfection was on the right side, and in twelve on the left. Dr. Marshall states, that in the examination of 10,800 recruits, he had found five in whom the right, and six in whom the left testicle was not apparent. In two of these cases there was inguinal hernia on the side where the tes ticle had not descended. t He met with but one instance in which both testicles had not appeared. § The testicle sometimes remains permanently fixed in the situation in which it is placed at birth ; but in some instances th,.: passage, though delayed, is completed at some period previous to puberty, and often within a few weeks after birth. Mr. Hunter was of
opinion that this completion most frequently happens between the years of two and ten.* Of the twelve cases mentioned by Wrisberg, in which one or both testicles were retained in the abdomen, in one the descent took place the day of birth, in three on the day after, in three others on the third day, in two instances on the fifth day, and in one on the twenty first day : in the other cases, the testicles had not appeared at the fourth or fifth week after parturition.-1- My own observations lead me to believe, that if the passage does not take place within a twelvemonth after birth, it is rarely fully and perfectly completed afterwards, without being accompanied with rupture. For the causes which operate at this late period tend as much to promote the formation of hernia as the transition of the testicle. In cases where the testicle makes no appearance before puberty, uneasiness is often experienced at that period, owing to the enlargement of the gland being restrained by the rings and parts composing the inguinal canal. At the same time also, it is often protruded outside the external ring by the movements of the abdomen in respiration.
The causes of a failure in the transition of the testicle have not been much investigated, and as considerable doubt has long prevailed respecting the mode and agency by which this change is effected, no satisfactory explana tion could be expected of the circumstances interrupting or preventing it. When we re flect on the nature of that process, as my researches have led me to describe it, it is clear, that there must not only be a perfect adaptation of parts, a due relation between the body displaced and the structures which it traverses, but also corresponding power in the agent by which it is accomplished. There are few muscles in the human body whose development in different individuals varies in a greater degree than that of the cremaster. And if such be the case after birth, it is not unreasonable to presume that similar differ ences exist in the fcetus before the gland changes its position, and that a failure in the process may be the result of deficient power in the museuhis testis to accomplish the pas sage. It is not improbable that this muscle is sometimes paralysed, and that the faulty transition is owing to a want of a due supply of the nervous energy, which we know is often denied to other muscles during foetal exist ence, and is the cause of deformities in the feet and other parts, with which infants are often uF:iered into the world. I think, indeed, we may fairly enumerate paralysis and defective development of the cremaster amongst the presumed causes of the imperfect transition of the testicle. Peritonitis occasionally at tacks the foetus in utero r, and produces ad hesions between the various abdominal viscera. It is well known that in congenital hernia the testicle is frequently united to a portion of intestine or omentinn, and that the formation of these adhesions previous to the transition of the testicle is sometimes the cause of the displacement, the viscera being drawn, together with the gland, into the scrotum. Many facts seem to show that similar adhesions are, on the other hand, an occasional cause of the temporary and permanent retention of the testicle, the crcmaster being insufficient to overcome this obstacle to its passage.