DETERMINATION OF PHYSICAL MATURITY 407 



THE AGE OF FIN WHALES AT PHYSICAL MATURITY 



THE DETERMINATION OF PHYSICAL MATURITY 



The fused or imfused condition of the vertebral epiphyses has been used as an index 

 of physical maturity. The method employed is essentially that described in the Report 

 of 1929 on p. 447. While the vertebral column is being turned during the process of 

 stripping away the muscles, the ventral surface is exposed, and by cutting the edges 

 of the vertebrae the state of fusion can be gauged at a glance. Owing to conditions on 

 the flensing plan and the rapidity with which the whales are disposed of, there is rarely 

 time to examine more than three or four vertebrae of each whale, even when using an 

 axe for the work instead of the knife that was tried at Saldanha Bay in 1926. 



The presence of a layer of cartilage between epiphysis and centrum is a sign that 

 fusion has not occurred. Towards maturity the cartilage layer becomes very thin, and 

 can sometimes be traced by the cracking away of splinters of centrum from epiphysis 

 or vice versa. After ankylosis a whitish line marks the join, but this eventually dis- 

 appears and no sign of fusion can be seen. Enumeration of the vertebrae has always 

 been done by counting forward from the ist caudal, which can easily be recognized 

 because the first of the ventral chevron bones is situated between it and the 2nd caudal. 

 As a routine one vertebrae at the posterior end of the lumbar series was examined 

 (ist caudal, 15th or 14th lumbar), one vertebra in the middle of the lumbar series, 

 one in the posterior thoracic region, and one or two as far forward as possible, i.e. the 

 2nd, 3rd or 4th thoracic. Usually the opposed ends of two vertebrae were cut, but no 

 difference was noticed between the state of fusion at the posterior end of one vertebra 

 and the anterior end of the next. 



Although the cervical vertebrae of Fin, Blue and Sei whales are neither wholly nor 

 partly coalesced into a cervical mass as they are in the Right whales and many toothed 

 whales, they are thickly enclosed in connective tissue and, for this reason, it was not 

 found possible to examine them on the plan in the limited time at our disposal. 



Following the statement of Flower (1864) that ankylosis begins from the ends of the 

 vertebral column and proceeds towards the middle, the posterior lumbar vertebrae were 

 at first considered diagnostic of complete maturity. Thoracic (dorsal) vertebrae were 

 examined at the same time, however, and it soon became evident that the lumbar 

 epiphyses might be ankylosed while the thoracics were still separated from their centre 

 by thin cartilage. 



Certain stages in maturity have been noted, but we have not had the opportunity 

 of examining a complete column in the transition state. In a few whales the lumbar 

 vertebrae were fused while the thoracics were unfused; in some, when fusion had 

 occurred throughout the column, the join was visible in both thoracics and lumbars ; 

 in others it could be seen in thoracics only, and in still others no sign of the join could 

 be seen anywhere. 



