36 PRELIMINARY COLD STORAGE STUDIES. 



MICROSCOPICAL EXAMINATION. 

 FRESH EGGS. 



A hen's egg consists of a shell, two shell membranes, the albumen 

 or white of the egg, the yolk, and vitelline membrane. The shell 

 membranes consist of interwoven fibers (PL I). Those of the thicker 

 outer membrane are much the coarser (PL I, fig. 1). 



At the broad end of the egg the shell membranes separate to form 

 an air chamber, which increases in size as the moisture of the egg 

 evaporates. 



The albumen, or white of the egg, is fibrillar in structure and con- 

 sists of a dense portion next to the yolk and an outer, more fluid part. 

 The yolk is formed of alternate concentric layers of yellow and 

 white yolk. The yellow yolk forms the greater part and consists of 

 large spherical granular masses 20 to 109/* in diameter (PL II, fig. 1). 

 These masses when hardened in situ are polyhedral, owing to equal 

 pressure (PL III, fig. 1). The white yolk is found in a flask-shaped 

 mass in the center of the yolk, and in thin concentric layers which 

 alternate with thicker layers of yellow yolk. The structure differs 

 from the yellow yolk in having spheres of several different kinds 

 which are smaller than those of the vellow yolk 40 to 80yw in diameter 

 (PL II, fig. 2). 



The vitelline membrane surrounds the yolk and consists of very 

 fine fibrils. 



COLD-STORAGE EGGS. 



The first eggs examined in the cold-storage experiment were six 

 fresh eggs. These were normal when examined May 24, 1906, and it 

 was stated that the eggs were laid the day before. The next exami- 

 nation was made on a withdrawal of four eggs from storage, Sep- 

 tember 7, 3.5 months later, and nothing abnormal was noted, the 

 same being true of the withdrawal of January 7, 1907. Another 

 examination was made of the June, 1907, withdrawal, representing a 

 storage period of 12.6 months. At this time two eggs were examined 

 and appeared in general to be normal eggs, but in the yolks were 

 found small rosette crystals. It seemed that they were most fre- 

 quently found in the outer portion of the yolk. In one egg they 

 were of very rare occurrence. This was the first appearance of these 

 forms and they figured later in the description of the samples of the 

 withdrawal of October, 1907, the last examination made. At this 

 time the entire white of the egg looked watery; the part next to 

 the yolk, although denser than the outer part, had deteriorated. 

 The shell membrane appeared microscopically normal, as well as the 

 vitelline membrane. The yolk assumed a much flattened form after 



" By Burton J. Howard and E. A. Read, Microchemieal Laboratory. 



