8 G. CARL HUBER 



the observations made on sections, as will be discussed later. 

 By cutting the oviduct at about its middle, freeing it from its 

 mesosalpinx and cutting the uterus about 1 cm. below the in- 

 sertion of the oviduct, a pipette fitted with a rubber bulb and 

 filled with warm normal salt solution can be inserted into the 

 uterine cavity and moderate pressure made. It is usually possible 

 to wash into a watch crystal a certain number of the contained 

 segmenting ova. Before reading the article by Widakowich, 

 essentially the same method as employed by him, for isolating 

 implanted blastodermic vesicles was developed. This may be 

 quite readily done after fixation in Carnoy's fluid and teasing 

 under a stereoscopic binocular. Vesicles sectioned in situ, 

 however, gave on the whole more satisfactory results, so that 

 teasing out implanted vesicles was not resorted to. 



The fixed tissues were imbedded in paraffin, using xylol as 

 a clearing fluid. For stages including those falling within the 

 period ranging from the first to the fourth day after insemination, 

 the ovary and oviduct to its insertion in the uterus, were em- 

 bedded en masse. For stages falling within the period of fifth 

 to sixth day after insemination, the uterine horns were divided 

 into segments measuring about 1.5 cm., and sectioned parallel 

 to the plane of the mesometrium. For later stages, after the 

 enlargements in the uterine horns are distinctly evident, these 

 were removed and cut severally in the three planes. The great 

 majority of the sections were cut at a thickness of 10 n ; certain ones 

 at a thickness of 5 /x ; a few at a thickness of 7 p. The sections were 

 fixed to the slide by the water-albumen method. The great ma- 

 jority of the series were stained in hemalum, counterstained in 

 Congo red. This solution, which presents certain advantages as a 

 counterstain for embryologic tissues, is prepared as follows: 0.5 

 gms. of Congo red (Griibler) is placed in 100 ccm. of distilled 

 water and the water brought to boiling. This should give a clear 

 solution. Before cooling, add 100 ccm. of distilled water and 

 10 ccm. of absolute alcohol. The Congo red solution thus pre- 

 pared may be kept many weeks. After staining the series in the 

 usual way in hemalum, they are differentiated in acid alcohol, 

 and passed through several washes of 'tap water' into distilled 



