344 



Prof. Farmer, Messrs. Moore and Walker. [Nov. 17, 



elements. The number of the chromosomes furnishes a far more important 

 criterion. It is seen that a large number of dividing nuclei contains less than 

 the normal complement of chromosomes. We have made a number of careful 

 counts of the chromosomes in numerous cases of carcinoma, and always with 

 the same result. In especial, we are indebted to Mr. L. Eobinson for his 

 assistance in this somewhat trying task. He has estimated the chromosomes 

 in 400 dividing nuclei, taken (100 from each) near the actively growing 

 regions of three different carcinomata originating respectively from the rectum, 

 scrotum, penis, and in an example of deciduoma malignum. 



In every case we find two well-defined maxima, one set of nuclei containing 

 32, the other 16, chromosomes. For purposes of comparison he has counted 

 chromosomes of the testis of the cockroach (Curve F), so as to obtain a control 

 indicating the probable degree of accuracy represented by the estimations in the 

 cancer nuclei. The same two maxima are, of course, apparent, but there is a 

 similar average error around the maxima, due to the difficulty of the actual 

 counting, and also the chance that some of the chromosomes might be absent 

 from the section, or that a limited degree of variation may really occur. And, 

 having regard to the fact that in the human species the chromosomes are not 

 easy, even under favourable conditions, to estimate very accurately, whereas 

 in the case of the cockroach the observer encounters far less difficulty in 

 this respect, the results may, we think, be described as satisfactory. For 

 although, after what we have said, it is obvious that, owing to amitosis, 

 and especially to pluripolar mitosis, a considerable extent of variations is 

 to be anticipated, the grouping of the numbers around the maxima of 

 32 (somatic) and 16 (reduced) is quite unmistakeable, as is shown in the 

 accompanying curves. 



15 20 25 



Number of chromosomes 



35 40 45 



Carcinoma of Eectum. 



The ordinates represent the number of cells that contained any given number of 

 chromosomes, as indicated by the abscissae. 



A. Cancer of the Eectum. — The hypochromatic nuclei to the left somewhat obscure, the 

 maximum at 16. The grouping of numbers about 24 and 64 are fairly well 

 shown. 



