Destructive Distillation of Animal Substances. 223 



improbable, that we may, without much hesitation, pronounce 

 against them ; and if so, the probable formula? of pyridine are 

 reduced to those marked with an asterisk. The question for 

 consideration is, whether even these can be supposed to represent 

 the constitution of the base in a feasible manner. On this point 

 no experimental evidence can at present be adduced ; but taking 

 into account all the circumstances connected with them, my 

 impression is, that none of them give the rational expression of 

 its constitution, and that pyridine and its homologues belong to 

 a class of bases of which we have as yet no other examples. 



In illustration of this opinion, it is necessary to enter into 

 some details regarding the constitution of the bases generally. 

 It is scarcely necessary to remind the reader that when Hofmann 

 described his two new series of volatile alkaloids, he applied to 

 those already known the name of amide, and to the new series 

 those of imide and nitryle bases. This nomenclature, which has 

 been more than once employed in the preceding pages, was 

 founded on the analogy in constitution of those substances with 

 the well-known amides, imides, and nitryles. A very little con- 

 sideration, however, suffices to show that this analogy is by no 

 means complete. The first series of bases may be correctly 

 compared to the amides, but the other two have no close resem- 

 blance to the imides and nitryles. On the contrary, they are 

 strictly comparable with the secondary and tertiary amides 

 recently described by Gerhardt and Chiozza, which are formed 

 from the primary amides by a process similar to that employed 

 by Hofmann to produce his two classes of bases. The closeness 

 of this analogy may be seen from the subjoined comparison of 

 these methyle bases with the benzoyle amides. 



Methylamine. Bimethylamiue. Trimethvlamine. 



C 2 H 3 i C 2 H 3 -i C 2 H 3 V 



h kN c 2 h 3 In c 2 h 3 In 



H J HJ C 2 H 3 J 



C 14 H 5 2 ^ C 14 H 5 2 ] C !4 H 5 2 ] 



h In c i4 h 5 o In c i4 h 5 o 2 ^n 



H J H J C 14 H 5 2 J 



Primary benzamide. Secondary benzamide. Tertiary benzamide. 

 From which wc see that in every case hydrogen is replaced, atom 

 for atom, by a compound radical, the only difference being, that 

 in the one set of substances the ammonia retains, in the other it 

 loses its basic properties. 



Hut the constitution of an imide or a nitryle is materially 

 different. Of the former, indeed, we know too little to admit of 

 any satisfactory conclusions regarding their constitution j but 

 taking benzonitryle with the formula C 14 IP N, as an example of 



