SUSCEPTIBILITY TO TRANSPLANTABLE TUMORS 79 



2. Methods 



a. Inoculation and observation. The methods used in trans- 

 ferring the tissue from one host to the other are those commonly- 

 employed. Ordinary precautions of asepsis were used. It 

 has already been shown (Crocker Laboratory) that tumor sus- 

 ceptibility is not influenced by the manipulation of the tissue 

 during the transfers. The mouse possessing the tumor was 

 first carefully shaved around the site of the proposed incision. 

 The approximate volume of the mass was then determined by 

 palpation and recorded. The instruments employed were 

 sterilized by being placed for a few moments in boiling water. 

 The mouse was etherized as lightly as was possible consistent 

 with relaxation. A straight incision of about three-fourths 

 of an inch was then made by means of curved scissors. By 

 manipulating two pairs of forceps around the tumor, the con- 

 nective-tissue strands that anchor the tumor to the skin and 

 body wall of the mouse can be severed. A small amount of 

 hemorrhage usually occurs. The blood may be removed by a 

 moistened piece of absorbent cotton. The operation was 

 performed with as much speed as possible — ^the time element 

 being one of the important factors of success, especially when 

 the mouse has two tumors to be removed. Complete extirpa- 

 tion of the mass was frequently obtained, this being a distinct 

 advantage, since the mouse can then be used for breeding after 

 its susceptibihty has been tested. The tumor mass was then 

 placed in a weighed sterilized Syracuse watch-glass to determine 

 the actual weight of 'type' masses. 



h. Measurement of size of tumor. Several methods have 

 recently been employed in determining the rate of growth of 

 the tumor mass. The older method (used by Bashford, Murray, 

 etc.) was to compute the interval between inoculation and the 

 time at which the tumor reached the inoculating point. The 

 procedure gives a rough approximation concerning the time 

 required to reach a given size when a series of tumors are to be 

 compared. It does not, however, give any evidence of the 

 successive growth points before this end point is reached. By 



