SKELETAL MUSCUI^ATURE OP THE KING SALMON. 

 FIvEXOR CAUDALIS VENTRALIS SUPERIOR. 



47 



This caudal flexor is a rather broad group of fibers which arises from the ventral 

 surfaces of the centra and the bases of the hemal spines of the last two vertebrae of the 

 peduncle, also from the base of the spine and the ventral surface of the lateral process of 

 the most anterior caudal vertebra. The fibers run slightly ventralward as they proceed 

 to their insertion into the bases of the fifth to the eighth caudal rays below the axial ray. 



The contractions of this muscle lead to a flexion of the lower half of the middle 

 portion of the caudal fin, and of the ventral caudal lobe. The tension in this case is 

 brought primarily on the uppermost rays of the ventral lobe. The muscle presumably 

 acts in conjunction with the next to be described. 



FLE.XOR CAUDALIS VENTRALIS INFERIOR. 



The origin of the inferior ventral flexor is from the surfaces of the last three hemal 

 spines of the caudal peduncle. The attachment is in a line which begins somewhat 



ventral to the anterior limit of origin 

 /• J {^' y/^^// of ^^^ preceding muscle and runs 



posteriorly and toward the trans- 

 verse process of the first caudal ver- 

 tebra. The fibers of the border of 

 the superior muscle arise under the 

 ventral border of the preceding 

 muscle. 



The fibers of the inferior flexor 

 run ventrally and caudally to inser- 

 tions into the bases of the last two 

 long ventral caudal rays and into the 

 adjacent series ofrudimentary rays. 



Contractions of this muscle 

 sharply flex the extreme ventral 

 border of the ventral caudal lobe. 

 Contraction at the same time with 

 the superior ventral flexor would 

 sharply flex the whole ventral half 

 of the caudal fin toward that side on 

 which the contraction occurred. 



Fig. 6. — The deep caudal fin muscles. /. t. spf-, flexor caudalis ventralis 

 superficialis; /. -v. spr., flexor caudalis ventralis superioris; /. v. i., 

 flexor caudalis ventralis inferioris; a. -.'.. adductor caudalis ventralis; 

 /. d. s., flexor caudalis dorsalis superior; /. d. i., flexor caudalis dorsalis 

 inferior; int., interfilamenti caudalis. 



ADDUCTOR CAUDALIS VENTR.\LIS, THE ADDUCTOR OF THE DORSAL CAUDAL LOBE. 



This muscle is a relatively thin and broad sheet of muscle fibers lying below but 

 in its body closely parallel with the caudal vertebral axis. The origin of the muscle is 

 revealed by cutting away the posterior portion of the superficialis, the major portion 

 of the interfilamenti caudalis, and the superior border of the superior ventral flexor. 

 It has a rather broad line of origin extending from the lateral spine of the first caudal 

 vertebra directly posterior to the second caudal ray below the axial ray. The tendon 

 of origin is rather thickened at the spine. The line of origin is along the dorsal margin 



