—No feasible plan has been devised for practising inoculation experiments upon human beings. It is known, however, that the disease may be transmitted in some cases among animals of the same species, and the transfer has been made in a few instances from man to the lower animals. In the Gratwick Laboratory (Buffalo) the disease has been thus transmitted through hundreds of mice, and has thus afforded the best means of studying it in its varied phases, albeit in small animals, ever yet enjoyed. But cancer does occur in animals and has proved to be capable of inoculation, and, therefore, has responded to one of the severest tests of the value of the theory. Moreover the facts cited above (under 4) are essentially successful auto-inoculation.
7. Clinical Observations.
—Add to the features already mentioned above those impressions which come from accurate observation and correlation of the phenomena attending many cases of cancer, and a plausibility is thus lent to the parasitic theory which it can never gain from study in the dead-house or through the microscope. The resemblance between it and other known infections, the local and general alterations of tissues and fluids, the chemical changes by which the cachexia of the disease is brought about—these with other features all conspire to give the keen observer of cases of cancer an impression of parasitism or infectiousness which nothing can efface. Add to these its endemic, sometimes almost epidemic occurrence, its apparent transmission by contact, and the fact that it is but little influenced either by nutrition or drugs, and the argument is still strengthened. As against these arguments little has been advanced save denials or negations.
In thus upholding the parasitic theory, the writer would not wish to be understood as claiming either that the parasite has yet been discovered or its nature positively made out, nor that it is a question of one organism alone; rather, on the contrary, he feels that it is probably a question of several agents, probably of protozoan character, perhaps too small to be recognized with the lenses of today, perhaps belonging to some as yet unstudied class of organisms, making themselves known, however, as do the hypothetical parasites of syphilis and scarlatina, by their effects. To accept the parasitic view is to reconcile many discrepancies of earlier times and to give an entity to the disease by which, and until something better be found, we may be more safely guided in its management.
The parasitic theory lends plausibility to the statement which the writer wishes to emphasize, that cancer, like many of the other infectious diseases, is at first a local condition, that it is not transmitted by inheritance, and that there is a time in the history of every cancer when, if it could be recognized sufficiently early, and if it were also accessible and thoroughly removed, it could be cured.
Nomenclature.
—The nomenclature of tumors has been much confused, and if some new terms are introduced it is perhaps better than to cling to some which have prevailed in the past. Various systems have been followed of naming them according to their supposed nature or their evident tendency, or according to some purely arbitrary classification; thus there is the distinction into homologous and heterologous or heteroplastic, according as they are similar to or variant from that tissue in which they seem to originate; or they have been referred to as benign and malignant according to the disposition which they evince; and these terms are in sufficiently frequent use to demand acceptance. The distinction between benign and malignant is convenient and in some respects accurate, implying little in regard to histological structure, but much in regard to their effect upon the individual.
So far as method of classification goes, the anatomical (i. e., the histological) has proved far the most satisfactory, and is that which is now generally adopted. It is the basis for the classification followed in the ensuing pages. But even here it is impossible to maintain abrupt or always accurate distinctions, because tumors are frequently of mixed type, and it is required, if desired to express their composition by their names, to sometimes combine words in an awkward fashion.
By common consent that tissue which predominates furnishes the concluding portion of the compound term, while by prefixing other terms we endeavor to imply the composite character of the neoplasm.
Thus we have osteochondroma, fibromyoma, myofibroma, etc., and it is necessary often to reduplicate terms in order to be accurate in description. While this complicates phraseology, it nevertheless furnishes to the reader a reliable clue as to the general character of such a growth; and if one reads, for instance, of a myxochondrosarcoma, he promptly infers therefrom that thereby is meant a tumor essentially a sarcoma, in which both myxomatous degeneration and cartilaginous formation have taken place.