SPINAL XERVES OF THE FROG. 119 



relative length, and has therefore not contributed to the 

 abnormality of the sacrum. This, seen from below, 

 has an undivided centrum almost double the normal 

 length of a single vertebra, and dissection shows that it 

 has two transverse processes on each side, both of which 

 on the left side support the ilium, and thus form a com- 

 pound sacrum, but on the right side the posterior one only 

 doing so. The neural arch is perforated by conspicuous 

 foramina which transmit the large nerve labelled viii. in 

 fig. 3. Above, there is a small but obvious single neural 

 spine, and immediately behind this is a deep transverse 

 trench, at the bottom of which is a harrow fissure partially 

 separating the arch into anterior and posterior portions. 

 Behind this trench the arch shelves sharply down to the 

 neural canal. This vertebra, peculiar as it is, so very 

 closely resembles another sacrum described by Howes, that 

 the above description and figure IV. should be compared 

 with his (No. 15, p. 269). There is this apparent excep- 

 tion, however — that in Howes' case the compound repre- 

 sented the true 8th and 9th vertebras, whilst mine is of 

 a 9th and an extra vertebra. 



The question now arises, how are the extra nerve and 

 vertebra to be enumerated — for it must be admitted that 

 the last vertebra is really a compound of two — there being 

 a duplicate transverse process, neural arch and nerve. 

 Taking Graupp's figure (No. 10, p. 165) of the spinal nerves 

 as a standard, it is at first somewhat surprising to note 

 that the whole lumbo -sacral plexus and the coccygeal 

 nerve are perfectly normal, except that the viiith 

 nerve in my specimen does not apparently contribute any 

 fibres to the N . crural is. As the urostyle and its nerves 

 are quite normal, and as in addition to the urostyle we 

 have a vertebral column of ten vertebrae and an extra 

 nerve, it is obvious that a vertebra and a nerve have been 



