DESTRUCTIVE DISTILLATION OF ANIMAL SUBSTANCES. 231 



member of the series, it is obvious that the ten equivalents of carbon and five of 

 hydrogen which it contains must be distributed among these three substances ; 

 and although we cannot, without further researches, determine how they are 

 distributed, it is at least sufficiently obvious that the choice among different spe- 

 culative arrangements is by no means large. In fact, our knowledge of the 

 laws governing the constitution of organic compounds, enables us to see that the 

 total number of possible permutationsf of the elements of pyridine is only eight. 

 They are as follows: — 



C 4 H,| C 4 H 3 ) C 4 H) C 4 H) 



C 4 H Q VN c 4 hn c 4 hVn c 4 h 2 >n. 



C 2 H") C 2 H ] C 2 H 3 ) C 2 H 2 ) 



c 6 h 2 ) c 6 h 3 ) c 6 rn c 6 H} 



C 2 HlN C 2 HfN c 2 hVn c 2 h 2 Vn. 



C 2 H ) C 2 H j C 2 H 3 J C 2 H 2 J 



Involving the existence of the following nine radicals, all, with the exception of 



methyl, at present unknown : — 



C 6 H 3 C 4 H 3 C 2 H 3 



C 6 H 2 C 4 H 2 C 2 H 2 



C 6 H C 4 H C 2 H 



Of these, two at least, C G H and C 4 H, are so extremely improbable, that we 

 may, without much hesitation, pronounce against them ; and if so, the probable 

 formulae of p}a*idine are reduced to those marked with an asterisk. The question 

 for consideration is, whether even these can be supposed to represent the constitu- 

 tion 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 p}'ridine 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 re- 

 garding the constitution of the bases generally. It is scarcely necessary to remind 

 the reader that when Hoffman 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 nitryl bases. This nomenclature, which has been more than 

 once employed in the preceding pages, was founded on the analogy in constitu- 

 tion of those substances with the well-known amides, imides, and nitryls. A 

 very little consideration, 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 resemblance to the imides and nitryls. 

 On the contrary, they are strictly comparable with the secondary and tertiary 



+ I assume, with Gerhardt, that the number of atoms of carbon in any radical must always be 

 divisible by two. 



VOL. XXI. PART I. 3 Q 



