THEORIES AND PROBLEMS OF CANCER 229 



the cases of small superficial cancers which are cured in the 

 same way. At the present time the only reasonable chance 

 of producing a cure is that afforded by the total removal of all 

 the cancerous cells. This can frequently be done successfully 

 in superficial cancers which are recognised early ; it is not 

 commonly possible in cases of internal cancer, which are gener- 

 ally not recognised until the cancerous cells have multiplied 

 and migrated to an extent which makes their total extirpation 

 an extraordinarily difficult if not an impossible achievement. 

 In connexion with reports of cures it must be remembered 

 that very occasionally a case of cancer recovers without treat- 

 ment and that a certain diagnosis is often impossible without 

 a microscopic examination of a portion of the growth. Even 

 when such an examination is possible the diagnosis is some- 

 times doubtful, as the chronic inflammatory condition seems to 

 merge almost insensibly into the malignant. Reported cures, 

 therefore, which are based entirely upon clinical evidence, are 

 to be received with considerable doubt, if indeed they be re- 

 ceived at all. Isolated recoveries following a certain line of 

 treatment must be regarded in the same way : serious con- 

 sideration can only be given if a number of recoveries follow 

 regularly upon a given treatment. 



A great deal of experimental work has been done with 

 animals in the hope of discovering a means of dealing with 

 cancer in the human subject ; practically all of this work has 

 been carried out with cancers artificially produced by inocula- 

 tions similar to those described in the last article. 



Certain kinds of resistance to the grafting of tumours usually 

 transmissible in mice have been demonstrated by a great many 

 observers. In 1889 Wehr 1 recorded the spontaneous cure of some 

 of his transplanted tumours. Subsequently Gaylord and Clowes 2 

 reported recovery to have occurred from 20 per cent, of the Jensen 

 mouse tumours ; many others have reported similar occurrences. 

 Gaylord and Clowes also found that the mice which recovered 

 were immune to a further inoculation and that 10 out of 30 

 were resistant to a third and more virulent tumour. Ehrlich 3 

 was successful in immunising mice against malignant tumours 

 by inoculating with a non-malignant tumour. Others have 



1 Arch. f. klin. Chir, Berlin, 1889, xxxix. 226. 

 3 Jo/ins Hopkins Hosp. Bull, Baltimore, 1905. 

 3 Arb. a. d. k. hist. etc. 1906, viii. 481. 



