124 CARNEGIE INSTITUTION OF WASHINGTON. 



in that it includes individuals from all age classes. In animals of a non- 

 susceptible race, the maximum reactive potentiality against a tumor is attained 

 by a gradual process at the period of sexual maturity. AVith advancing old 

 age non-susceptibility decreased somewhat. These data have a direct 

 bearing upon the nature of the individuality of the organism. The age- 

 cycle susceptibility curve for gonadectomized individuals is, as may be ex- 

 pected, the direct reverse of that for the normals. 



"Another point of minor importance is the fact that there is no differential 

 effect of gonadectomy upon the two sexes, thus indicating that the gonads 

 are a determining factor in the process of differentiation for both sexes. 



"The conclusions to be drawn from the complete experiment naturally 

 group themselves under two headings: {A) the activity of the tumor cell; 

 {B) the reaction of the host. 



"(A) The activity of the tumor cell. (1) There is, in some cases at least, 

 a uniform reaction, providing the tumor is transplanted into individuals of 

 the same age and sex of a relatively homogeneous series of hosts. In other 

 words, no rhythms of tumor growth are encountered. (2) A transplanted 

 tumor grows progressively (within limits) at a fairly uniform rate of develop- 

 ment if placed into definitely proven homogeneous mice (dBr stock and Fi 

 hybrids). Sudden fluctuations in growth activity may sporadically occur, 

 due to a process analogous to mutation. 



"(B) The reaction of the host. (1) Race is the primary factor that de- 

 termines whether or not a given individual shall or shall not grow the tumor 

 mass progressively. Susceptibihty and non-susceptibility are manifestations 

 of the genetic constitution of the individual. (2) Several secondary physio- 

 logical factors, among which age is the most important, function in determin- 

 ing the outcome of a given reaction. These may be called contributory or 

 accessory factors. (3) The age factor is an expression of the degree of the 

 process of the assumption of tissue specificity controlled to some extent by 

 the activity of the gonads. (4) The age-susceptibility curve towards trans- 

 plantable tumors for normal individuals of a non-susceptible race bears a 

 remarkable simiUarity to the curve of activity of the gonads. (5) The sex 

 factor (encountered especially with young mice in development) depends 

 upon at least two primary causes: (a) the age factor, and (6) the difference 

 in physiological activity between the sexes at the different age-periods of 

 life. (6) Removal of the gonads does not change the massed percentage 

 reactions for individuals of a non-susceptible race. This bears out the previous 

 conclusions that the number of percentage reactions in a given strain depends 

 upon the genetic constitution of the individuals. (7) Gonadectomy produces, 

 in the stock emploj^ed, a significant increase in percentage reactions in mice 

 attaining sexual maturity (age class 3). (8) Gonadectomy causes an approach 

 towards a neutral type (loss of characteristic differences between sexes) in 

 the percentage of reactions towards both tumors used, just as it does in the 

 case of morphological characteristics (Hatai and others). (9) By the removal 

 of the gonads, the individuality of the tissues and the normal functioning of 

 the age factor can be interfered with. (10) A severe shock, caused by such 

 an operation as gonadectomy, produces, in some cases at least, a resistant 

 state to transplantable tumors that is at its maximum from 5 to 10 days 

 after operation." 



Receipt of sarcoma 180 from the Crocker Research Fund. — During 

 the early summer, mice with implants of Crocker Fund sarcoma 

 180 were received by this Department, through the kindness of Dr. 

 F. C. Wood, the director of the Crocker Research Fund. Preliminary 



