GENERAL REVIEW OF THE INVESTIGATION. 105 



kind to become crystalline. In the course of a few months eggs 

 which are kept in cold storage are found to develop small rosette 

 crystals in the yolks. These, it has been found, occur most frequently 

 in the outer portion of the yolk. The size of the crystals is found to 

 be from 18 to 109/* in diameter, and the form is shown in Plate III. 

 The exact character and composition of these crystals has not yet 

 been ascertained, as they constitute a relatively small percentage of 

 the entire mass, and hence their isolation in sufficient quantities for 

 analysis is attended with extreme difficulty. Many attempts, as 

 has been seen from the detailed statement in the preceding section 

 of this report, have been made to isolate and prepare these crystals 

 for identification. It is perhaps possible that they belong to the 

 class of substituted fatty bodies, but no definite statement can be 

 made except that it seems that they are not tyrosin. The observa- 

 tions of these bodies seems to be entirely new, as no account has 

 been found of them in other publications. It is probable, therefore, 

 that their existence may be regarded as one of the means of distin- 

 guishing eggs which have been a considerable time in cold storage 

 from fresh eggs. 



CHICKENS. 



Quite as important, and perhaps even more instructive than the 

 studies relating to bacterial growth at low temperatures, are the 

 studies of the changes which take place in the tissues of the material, 

 and which can be recognized under the microscope. Changes in 

 tissue are usually due either to fermentation or to enzymic action, if 

 the two terms are to be used in any different sense. It is generally 

 conceded by investigators at the present time that the actual changes 

 in the structure of the tissues are not so much due to direct action of 

 the bacteria as to the enzymic ferments which bacteria secrete or 

 produce or which exist in the normal cells of the tissue itself. Hence 

 the action of enzymes may be regarded as the last step of fermen- 

 tation. 



The studies in histological changes were undertaken on market 

 chickens which had been stored for varying lengths of time at about 

 13 F. One difficulty in connection with a general investigation of 

 this kind is that if chickens are selected at random, or purchased in 

 the open market after having been dressed, a good deal of uncer- 

 tainty must exist concerning their previous history and the condi- 

 tions to which they have been subjected. Commercially it is well 

 known that the interval which exists between the period of slaughter 

 and the period of storage is of varying length. The temperature 

 and other conditions of environment to which the slaughtered 

 chickens are subjected in this interval are far from uniform. The 

 method of transportation may have much to do with the character 

 and extent of the changes before cold storage in a warehouse begins. 



