98 OF REPRODUCTION. 



and an elongated portion; their head, which is sometimes oval or 

 almost circular, sometimes lozenge-shaped, at others resembles the 

 catkin of the bulrush; but as it is at the same time flattened, it can- 

 not be recognised, except when seen in front. Their point, some- 

 times straight, very long, and conical as in the dunghill cock, some- 

 times short and fine as in the dog, at others very long and flexuous, 

 pretty much resembles the tricocephalous worms, or the slenderest 

 worms that inhabit the human body. Upon the whole, the spermatic 

 animalcula has a general resemblance to the tadpole of the batracians; 

 its dimensions do not exceed one, two, or three hundredths of a mil- 

 limeter; it is not to be seen in the seminal liquor previous to the age 

 of puberty, nor in old men, nor in the interval of the seasons at which 

 certain animals copulate, nor in the mule, which, as is well known, 

 is incapable of reproduction; it is not met with in the matter furnish- 

 ed by the urethra, the prostate, or the seminal vesicles, and it is to 

 be found with the same characters in all those animals that are wholly 

 or partially deprived of these organs. It is produced by the testicle 

 which secretes it. Every prolific animal contains it in its prolific 

 gland, and frequently in its deferent duct. The movement of these 

 corpuscles seems to take place under the influence of a will; they 

 always move forwards; they can be killed by an electric discharge, 

 and thenceforth their motion ceases to be active. In escaping from 

 the formative gland, the viscous matter in which they are enveloped 

 is too thick to permit them to exercise any visible motion; but it is 

 only necessary to mix them with some other liquid, or permit them 

 to become diluted in the seminal vesicle or urethra, in order that their 

 mobility should come immediately into play. 



246. Simple microscopic globules, on the contrary, have neither 

 head nor tail, are round or of irregular shapes, sometimes larger and 

 sometimes smaller, and move only under the influence of some ex- 

 ternal impression, and without any determinate end. They exist in 

 all the fluids of the economy, in the blood, in the serum, in the milk, 

 even in the spermatic liquor, before puberty, as well as at all other 

 periods of life, and in all animals. 



247. MM. Prevost and Dumas by their numerous experiments on 

 artificial fecundation, became convinced that the animalcules alone 

 constituted the germ; they never effected a vivification when the 

 liquid they made use of did not contain them, or when these living 

 molecules had been killed or destroyed in any way, whereas fecunda- 

 tion took place whenever the liquor they employed contained even 

 a few animalcules. 



248. Although the experiments of these physiologists bear marks 

 of the greatest good faith and accuracy, I cannot, nevertheless, 



