PREFACE 
Since our research has been oriented for many years towards lung cancer, 
especially studies in etiology, we have been consistently seeking sensitive experi- 
mental animals. Such models should fulfill the following stipulations: 1. that 
lesions be induced within a survevable time period after administration of known 
carcinogens; 2. that well-differentiated tumor types (adeno- and squamous cell 
carcinomata) should originate in the respiratory tract; and 3. that no infectious 
diseases of the respiratory tract should interfere with the experimental results. 
About 10 years ago, our work was confined to the use of the Syrian golden 
hamster {Mesocricetus auratus) which had been recognized as the model for res- 
piratory tract carcinogenesis (Saffiotti 1969, 1974; Saffiotti, et ai, 1968; Althoff, 
et ai, 1971a, b; Nettesheim. 1972; Laskin and Sellakumar, 1975; Wynder and 
Hoffman. 1964. 1967; Delia Porta, et ai, 1958; Dontenwill and Mohr, 1961; 
Montesano and Saffiotti, 1968, 1970). This animal, however, frequently pre- 
sented with early tracheal papillomata, resulting in premature death by asphyxi- 
ation; consequently, the time required for induction of lung carcinomata, whose 
histopathologv would be significantly differential (adenocarcinoma, squamous 
cell carcinoma) could not be realized (Feron, et ai, 1972; Montesano, 1970; 
Lijinsky, et al., 1970; Haas, et al., 1973; Herrold and Dunham, 1963). More- 
over, the pulmonary tumors in this experimental animal have been suspected as 
originating from parts of tracheal papillomata ''transplanted'' to the lungs (Spit 
and Feron, 1975; Stenback, et ai, 1973; Creasia and Nettesheim, 1974). Studies 
on respiratory tract sensitivity to known carcinogens in Chinese hamsters led to 
mainly negative results, so that this animal species had to be rejected (Mohr, 
etai, 1966, 1967, 1970; Althoff, a/., 1971b; Reznik, a/., 1976a, b, c). 
VVe have finally verified that the European hamster, which lives wild in 
West Germany, fulfills the set stipulations for an animal model and that, in 
comparison to the .Syrian golden hamster (Fig. 0-1), offers additional advantages. 
With known nitroso- compounds, respiratory tract tumors have developed within 
a relatively short time of 13 weeks (Mohr, et ai, 1972); moreover, these tumors 
are for the most part well-differentiated. With corresponding doses of carcinogens, 
tumors are produced in all animals (100%) (Mohr, et ai, 1972, 1973, 1974a, b; 
Reznik-Schiiller and Mohr, 1975; R^mk, etal., 1977). 
The European hamster is comparable in size to the guinea pig and therefore 
offers sufficiently large anatomical dimensions for the execution of clinical test 
procedures (radiology, bronchography, cytology) throughout the period of tumor 
development (Freyschmidt, etai, 1975; Reznik, etai, 1975a; Eckel, etai, 1973, 
1 974a, b, 1 975). The value of such studies in determining early tumor recognition 
cannor be under-estimated. Moreover, Cricetus cncetus is quite appropriate for 
special treatment techniques such as intratracheal and intrabronchial instillation 
of a carcinogen; this procedure can be performed without difficulty and much 
more easily than in other rodents. It also appears that the European hamster will 
prove to be better for studies on inhalation because its tidal volume is larger than 
that of the Syrian golden hamster (Kmoch, et al., 1975; Reznik, et al., 1975b, c; 
Kmoch, et ai, 1976). Moreover, it has been demonstrated in inhalation experi- 
ments with labelled cigarette smoke that about 30% more particulate matter is 
deposited in the lungs of the European hamster than in the Syrian golden hamster 
