A system of obstetrics . anner tending to drive them to the place where there is mostmalic acid. It has also been found that malic acid is excreted by thefemale organs of these plants. Some similar process may occur in thehigher mammals and lead to a swarming of spermatozoa around the egg. Barry1 was the first who described spermatozoa within the zona pel-lucida of the mammalian ovum. His observations, made on the rabbit,have been confirmed, more than twenty spermatozoa having been seenwithin the egg-case by Hensen. According to Hensens observations on the rabbit, the spermatozoabegin to penet
A system of obstetrics . anner tending to drive them to the place where there is mostmalic acid. It has also been found that malic acid is excreted by thefemale organs of these plants. Some similar process may occur in thehigher mammals and lead to a swarming of spermatozoa around the egg. Barry1 was the first who described spermatozoa within the zona pel-lucida of the mammalian ovum. His observations, made on the rabbit,have been confirmed, more than twenty spermatozoa having been seenwithin the egg-case by Hensen. According to Hensens observations on the rabbit, the spermatozoabegin to penetrate the zona pellucida about thirteen hours after cells of the discus proligerus have by this time undergone a mucousdegeneration, and the vitellus has shrunk somewhat (from the expulsionof liquid), and has given off the polar bodies. Some of the sperma-tozoa enter the zona obliquely, and these never get through it; others 1 Phil. Trans. Boy. Soc., 1843. 100 PHYSIOLOGY AM) HISTOLOGY OF FERTILIZATION. Fio. enter it perpendicularly, and bore their way into the -pace between thecontracted ovum and the zona (Fig. 14). One of them enters th<protoplasm, and its head or nucleus may for a time be seen as the malepronucleus; this approaches the female pronucleus, and the two fuse toform the segmentation nucleus of the fertilized egg, which latter is hence-forth named the oosperm. From this fertilized cell, made up of food-materials stored in the vitellus, of protoplasm of the egg mingled with protoplasm from the tail of the sper-matozoon, and of a oucleus resultingfrom the fusion of the la-ad of thespermatozoon (male pronucleus) withthe residue I female pronucleus) of thegerminal vesicle of the ovum, thefoetus with all it- tissues and organsis developed by cell-multiplicationand cell-modification. The Origin of Tissues and Organsby Diffir<ntiaHon. — The fertilizedegg divides into a number of cells:these, at first alike, arrange them-selves into groups, and, cont
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
