DEVELOPMENT OF THE PIG DURING} FIRST TEN DAYS. 331 



method of procedure is the slow injection of the cavity of the 

 upper part of the uterus with some preserving fluid, and a 

 subsequent search through the contents under the microscope. 



Within a space of time after the death of the sow, varying 

 from three quarters of an hour to three hours, I very slowly 

 injected '25 or "5 per cent, chromic acid into the upper half or 

 third of the uterus, having previously tied up the upper end 

 of the piece of uterus. I allowed as much fluid to flow in 

 as was possible without running the risk of bursting the 

 uterus, in order that the folds of the mucous membrane should 

 be reduced to a minimum. In this way the ova were caused 

 to float freely in the fluid. 



The lower end, through which the injection had been made, 

 was then ligatured, and the whole was placed in '5 per cent, 

 chromic acid for two or more days. The contents of the 

 uterus were then let out into glass vessels, and the specimens 

 were easily found under the microscope. 



Chromic acid used in this way was found to be the most 

 satisfactory, on account of its clearness and the absence of 

 any precipitate. 



In a few cases I used Flemming's solution with equal success ; 

 but other fluids, such as Perenyi's, or solution of nitrate of 

 silver, were unsatisfactory, owing to the great precipitation 

 which occurs rendering the search for the embryos too 

 laborious. 



All my specimens were stained before they were cut into 

 sections. The stains used were hsemalum, carmalum, hsema- 

 toxylin, and borax carmine. They were embedded in paraflfin 

 by means of cedar oil. 



Material. 



The following account is based upon the examination of 

 about 100 embryos obtained from sixteen sows. In about ten 

 other sows I failed to find any specimens. The majority of 

 those X have no doubt were really pregnant. My specimens 

 raav be tabulated thus : 



