It is interesting that the normal undulating motions of the spermatozoa, where they lie together in regular masses without being able to change their position, very frequently coincide in a remarkable manner, appearing to be carried out, as it were, by one common will. I3ut although this may appear strange at the first glance, it cannot surprise us when we consider that the same behaviour is ob served in the ciliated cells. We here see the motions in the cilia of one epithelium regu lated, as it were, by one comnion plan ; we observe how these coincide with the move ments of the cilia of others, and thus unite into one regular motion of the whole. A peculiarly beautiful sight is afforded by the aggregate motion of the spermatozoa in the semen of the earth worm, which resembles the undulating motion of a corn field. Among the insects we have also various opportunities of observing this kind of aggregate motion.
A similar aggregate motion is frequently (especially atnong the Invertebrata) found in the separate bundles of spermatozoa, even when they are still surrounded by their cyst like enclosures. At first sight it creates an impression as if' an undulating fluid were agitated in the interior of the cysts, whilst it is merely the winding motions of the sperma tozoa, which follow each other in quick and regular succession, imparting the impulse to the whole mass.
Motion, hovvever, is entirely wanting when (as is especially the case among the insects) the spermatozoa are united into simple and uniform cords. A slight curving or trembling is only observed now and then, vvhich is evidently the consequence of hygroscopic conditions.
We know as little of the cause of the movements of the spermatozoa as we do, in point of fact, of the reinote cause of every mo tion. But that it depends on certain relations of structure and composition, is evident from the circumstance, that it is wanting in the unde veloped spermatozoa, only' gradually taking place with progressive developement. A slight vibration or beating with the tail is first of all observed in them. The most lively', most vigorous, and most combined motion takes place, on the other hand, during the period of rutting, when the developement of the fructi fying spermatic elements has reached its height.
But the motion of the spermatozoa is not even then unlimited. The death of' the ani mal in whose spermatic organs they are con tained, or their removal from it, only allovt s the motions of the spermatozoa to survive for a time, which, however, is of a different dura tion in different animals. It seems to be
shortest in the birds, where the motion fre quently is extinguished fifteen or twenty mi nutes after death ; at least it can but rarely be observed after some hours. In the main malia their motion survives some time longer, especially if they remain enclosed in their natural organs.
Death, or removal, seems to have a different influence on the spermatozoa of the cold blooded animals ; among the fishes, for in stance, they continue moving for day s after having been expelled from the body. The mode of death of the animals has no influence at all upon the duration of the motion in the spermatozoa. It remains all the same uhe titer the animals are decapitated, strangled, or poisoned.
The motion of the spermatozoa survives longest of all in the interior of the female generative organs. The insects (in whom, as in Gasteropoda and some other animals, parti cular pockets or capsular organs are deve loped during the period of procreation) furnish the most striking proof of this. The sperma tozoa, when enclosed in these, frequently re tain their full vitality for months. Among the mammalia, likewise, the motions of the spermatozoa remain unimpaired in the vagina, or in the uterus, for some days after copulation.
The mucous coat which covers these or gans has no prejudicial effect on the motion and vigour of the spermatozoa*, and equally as little so the addition of other animal fluids, as the secretion of the prostate, the serum, milk, &c. Common saliva, and even bile or pus, does not exercise any impeding influence upon the motions of the spermatozoa.
The addition of urine, especially when hav ing an acid reaction, seems to have a rather more injurious influence upon them, for their niotion ceases soon afterwards, although for some hours slight traces of it may still be per ceived.
We have already treated of the influence of common water upon the sperrnatozoa. Diluted saline solutions or sugar and water, on the other hand, either do not produce these inju rious effects at all, or, at least, only in a very slight degree. The chemical agents are the only ones which have a positively injurious effect on the spermatozoa, changing and destroying their structure and composition ; as for instance alcohol, acids, metallic salts, &c. Diluted aqueous solutions of narcotic vegetable substances, of strychnia, morphia, &c., have the same effect as common water.