The external form of the brain and the auditory sac appear very distinctly. When this is accomplished, remove all the absolute with a pipette and add pieces of solid paraffin to the chloroform. In the sections of the anterior region, L The lateral epiblast composed of several layers of columnar cells.
Especial attention should be paid in the earlier specimens to the masses of nuclei enveloped in protoplasm and connected with each other by protoplasmic processes; and in the later stages to the breaking up of these masses into blood corpuscles and the conversion of the protoplasmic processes into capillaries, with cellular walls.
Mr Threlfall, of Caius College, has recently elaborated a method of mounting sections which in our opinion has many important advantages over the shellac method. Foster, M. If osmic acid, which we believe will be found serviceable for these ear]y stages, is employed, it will be necessary to remove the blastoderm from the yolk before treating it with the reagent.
Recently however Messrs CaldweH and Threlfall have designed an automatic microtome which has been used with success at the Cambridge Morphological Laboratory and promises to effect a great saving of time and trouble in cutting sections vide p.
Two methods of hardening can be adopted at this age. It will be well to mention here that although a doe may have been satisfactorily covered, embryos are not always obtained from her. To make it, boil a strong aqueous solution of ammonia-alum with excess of carmine for 10 to 20 minutes, filter, and dilute the filtrate until it contains from 1 to 5 p.
Both these incubators consist essentially of a large water-bath fitted with a gas regulator. From this it must be removed into alcohol of 70 p.
The transference may easily be effected, if both the watch-glass and slide are plunged into a basin of clean warm salt solution.
One of these involves the removal of the blastoderm from the yolk, as in II. We have not found that corrosive sublimate gives such good results as picric acid in the case of chicks and mammalian embryos. By this means shrinkage and distortion are avoided, the glycerine becoming very gradually more and more dense. The epiblast in the median line one layer thick and in the form of a groove medullary groove.
Zoologischer Anzeiger No. These are to be removed from the egg, in the usual way vide II.
The chief point to be noticed is the more rapid segmentation of the central than of the peripheral spheres. Care must of course be taken that the embryo itself does not become at all dry.
She should never be allowed to want for water, and should be well supplied according to her appetite with soft food. The best hens lay once every 24 hours, and by observing the time they usually lay and they generally lay pretty regularly about the same time , a fair guess may be made beforehand as to the time the egg has been in the oviduct. The views from the two sides differ chiefly as to the appearance of the heart. Pour into the basin so much of a '75 per cent, solution of sodium chloride warmed to 38C.
When the sections are cut, place them in rows on a slide prepared in the following manner. Make a solution of white shellac in kreasote by heating, and let it be of the consistency of glycerine, or slightly more fluid. The paraffin block is pared in such a manner that the edge nearest to the operator and that opposite to him are parallel.