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fore to be taken as a whole ; and the vertebra having most to do with 

 its support can well be held homologous to the vertebra doing the 

 same in other spines. If we admit this vitalistic conception, we can 

 understand that there is a tendency for parts in corresponding situ- 

 ations to develop in a corresponding manner. Thus the penultimate 

 lumbar vertebra (the 23rd) has certain characteristics which may be 

 found when it is the 24th. Rosenberg fully recognizes this fact, but 

 I do not see that he öfters any explanation of its occurrence. The 

 action of the vital principle is also shown in moulding parts to 

 approach their normal conditions when some disturbing cause has 

 interfered with the usual course of development. Instances of this 

 will be given in the discussion of the spines. 



The next question to be settled is whether there heap re eise 

 number of human vertebrae. It certainly is very unlikely. Fol 

 has shown, and his discovery has been confirmed, that at a very early 

 time the human foetus has 88 vertebrae, some of which, however, do 

 not persist. It would require a much larger number of observations 

 than is likely to be made to convince one that the number 38 is 

 absolutely constant, or that even if it be, the same number always 

 come to maturity. In point of fact there seem to be no precise data. 

 Steinbach found that the usual number of coccygeal vertebrae in 

 the male is five, and in woman four or five. For my part I have 

 seen so many cases in which I was unable to say with certainty 

 whether or not certain nodules at the end of the coccyx represented 

 vertebrae, or certain constrictions a division between two, that I admit 

 my inability to count the coccygeal vertebrae in at least many cases. 

 According to all analogy it is very unlikely that there should be even 

 a fairly definite number. It is well known that variations in number 

 of the vertebrae of the different regions increase tailwards. All the 

 spine below the vertebrae supporting the ilium, has but a very sub- 

 ordinate function, and consequently is in an unstable condition. The 

 importance of this question is on account of the objection to the theory 

 of inter- or ex-calation or irregular segmentation, that it cannot be 

 proved that certain elements normally on one side of the sacrum have 

 not changed their position. This is true enough; but when the vertebrae 

 at the borders of certain regions are characteristic ones and yet there 

 is an abnormal number between them the objection does not seem 

 weighty. 



The type. The study of this question, absolutely independent 

 of the point of view, brings more and more vividly before my mind 



I 



