'."riien fine-grain photograpliiic films are 

 used, a binocular microscope is most suit- 

 able as tiie grain size of the film permits 

 greater magnification of the vertebrae with- 

 out loss of contrast. 



COST AMLTSIS 



The X-ray machine used by the Menhaden 

 Investigations vjas assembled from used com- 

 ponents at a total cost of approximately 

 $550.00. Standard diagnostic machines witli 

 an equivalent kilovoltage range (25 to 100 

 kv.) from X-ray equipment manufactui-ers 

 ■would cost somewhere between .pi, 000 and 

 $1,500 new. This price would preclude cost 

 of installation and necessary shielding. 



In fish radiography, the expense of 

 filming and developing is incidental, pro- 

 i-d-ding usual darkroom facilities are avail- 

 able. For example, the cost of radiograph- 

 ing m.enhaden specimens by this investigation 

 is estimated at about $25.00 per 1,000 fish. 

 This includes the purchase of X-ray film., 

 film holders (cassettes), developing and 

 fixing chemicals, and lead wire for identi- 

 fjT-ng exposed films. 



AGKNO'JLElJGME'nS 



The construction and technical devel- 

 opment of the X-ray machine used by the 

 I'enliaden Investigations was accomplished by 

 Mr. G. G. Barton, Electronics Engineer, 

 liachjine and Supply Company, Beaufort, North 

 Carolina. 



Thanks are due to various members of 

 the staff of the Menhaden Investigations for 

 the many valuable suggestions offered in the 

 development of successful radiographic tech- 

 niques. 



llote: Those interested in adopting the X-ray 

 method are urged to read the following refer- 

 ences for further information on the use of 

 low-vcltage radiation for various research 

 problems : 



ALEXANDER, A. E., AND H. F. SHEKTOOD 

 19iil. Radiography of culture and 



material parts. Photo Technique, 

 March 19lil, pp. 50-52. 



ANONYT'IOUS 



1938. Stereoscopic soft X-ray 

 examination of parchment 



antiphonaries . Technical Studies 

 in the Field of Fine Arts. Harvard 

 Uiiv., Hilliam Hays Fogg Art Mus., 

 vol. 6, no. 4, pp. 277-280. 



CLARK, G. L. 



19 lO. Applied X-rays. McGraw Hill 

 Book Company, New York, 67U pp. 



SUHJ'IARY 



1. Radiographs provide an efficient means 



of determining vertebral nuribers in fish. 



2. Diagnostic X-ray machines having a kilo- 

 voltage capacity of approximately 25 to 

 100 kv. appear to be most suitable for 

 fish radiography. 



3. Standard X-ray film was found to be 

 sati sfactory for X-raying menliaden spe- 

 cimens larger than approximately 35 mm. 

 fork lengtii. 



ii. Fine- grain photographic film, such as 

 Kodalith, used in combination with a 

 paper cassette, was foujid to be satis- 

 factory for resolving incompletely 

 ossified vertebral columns of larval 

 menhaden approximately 2U mm. in length. 

 Also, successful resolution of vertebral 

 columns of pompano, 13 mm. standard 

 length, and mullet, 18 mm. standard 

 length, was achieved with this type 

 film. 



5. The X-ray machine used by the Menhaden 

 Investigations was assenbled from used 

 components at a cost of apnroximately 

 $550.00. 



6. The cost of routine X-raying of menhaden 

 specimens for vertebral counts is esti- 

 mated at about $25-00 per 1,000 fish. 



LITERATURE CITED 



BAILEY, REE7E ¥.., AND W. A. GOSLINE 



1955. Variation and systematic signifi- 

 cance of vertebral counts in the 

 American fishes of tlie family Percidae. 

 Museum of Zoology, University of 

 Michigan, Misc. Pub. No. 93, UU pp. 



BONHAM, KELSHAW, AW W. H. BAILIFF 



1953. Radiography of small fishes for 



meristic studies. Copeia, no. 3, 

 pp. 150-151. 



