370 Transactions of the Society. 



Both processes in retrogression can best be studied in the bodies 

 of rats and mice or other small mammals ; indeed the latter process 

 can only be studied well in such subjects. Flemming and others 

 have starved dogs and other large mammals for a long period, with 

 the result that they have failed to observe the most interesting and 

 essential part of the process. In rats and mice, more especially the 

 latter, which are often trapped in a starving condition, the system 

 seems to be so exceedingly sensitive to excess or deficiency of 

 nutrition, that they may either fatten or starve within the space of 

 twenty-four hours; the Httle animal from which Figs. 9, 11, and 

 12 were drawn, was found almost dead in a jar, into which it had 

 fallen, and in which it could not have remained above twenty-four 

 hours, yet the whole of the difierent stages of retrogression in fat- 

 cells could be followed upon one preparation of its mesentery. 



This great susceptibility to variation in nutrition is apt to intro- 

 duce an element of uncertainty or confusion into the study of the 

 process of retrogression upon them, for it often happens that 

 the remains of fat-cells, which had been broken up some time 

 previously, are to be found in a preparation where well-developed 

 fat-tracts point to even excessive nutrition. The first changes, 

 during the absorption of the contained fat, seem to occur in the 

 condition of the fat itself, which, from being of a yellowish-white 

 colour and thick consistency, becomes more transparent, watery, and 

 sliglitly red in colour. These changes have been previously noted 

 by other observers, who have compared the resultmg fluid or fat to 

 serum, although there is nothing of the nature of serum about it, 

 for we find that under the action of osmic acid it blackens even 

 more intensely than in the case of newly formed fat. When once 

 absorption has faMy commenced, if nutrition continues deficient, 

 it follows a steady course, characterized by diminution of the fatty 

 contents and the contraction and thickening of the protoplasmic 

 envelope containing them ^ari passu vdth each other. This 

 process is illustrated by Figs. 7, 8, 9, and 10, showing different 

 stages in different animals of the process of fat-absorption from fat- 

 cells, and it will be found that in all the mammalia the process and 

 appearances are the same throughout. Fig. 7 is from the body of 

 a young man who died of cancer of the skin, under the care of one 

 of us, at St. John's Hospital. He had entered the hospital only two 

 months before his death, a plump and well-nourished individual, 

 and said that previously he had never had a single day's sickness. 

 His downward progress was rapid, as the whole of the skin of the 

 left side of the thorax became gangrenous, and during the last few 

 days of life he was kept under the influence of morphia, on account 

 of his suflerings, and as he took httle or no food latterly, he died 

 much emaciated. Fig. 7 represents a part of his omentum, taken 

 by permission immediately after death, and stained by silver and 



