546 
MR. SIBSON ON THE MECHANISM OF RESPIRATION. 
7 1 . In the Chameleon (fig. II.) there are external intercostals, whose fibres are 
almost vertical, superficial to the usual external intercostals (§ 14). 
7 1 . In the Rabbit (fig XI.) a supracostal muscle passes from the seventh rib to the 
eighth, ninth and tenth ribs. 
8.8 a. In the Porpoise (fig. VII.) a web of superficial fibres passes from the first 
and second to the third, fourth and fifth ribs (§ 74). 
9. The portions of the internal intercostal muscles between the costal cartilages. 
In Birds (figs. III. VI.) the muscles between the sternal ribs are joined to those be- 
tween the vertebral ribs (§§ 18.24). In the Porpoise and Calf (figs. VII. IX.), and the 
Monkey and Pig (figs. XV. VII. Archives of the Royal Society), the intercartilaginous 
portion of the internal intercostals are distinctly separated from the intercostal por- 
tions (§§ 48.49.61.85). In the Seal (fig. VII.) the first costal cartilage has a special 
elevator (§ 62). 
9 a. 9 b. In Birds (figs. III. VI.) and in the Chameleon (fig. II.) triangular muscles 
arise from the sternum and are inserted into the sternal ribs (§§ 23.15). 
10. The serratus posticus superior (§§ 52.64). 
10 a. In the Seal (fig. VIII.) there is an intermediate serratus posticus (§ 64). 
1 1. The serratus posticus inferior. In the Porpoise and Rabbit (figs. VII. XI.) the 
superior and inferior serrati are blended (§§ 53. 64.65. /5. 88). 
12. Sterno-mastoid (§§ 59.90). 
13. Sterno-hyoid (§§ 59.71-90). 
14. Sterno-thyroid (§§ 59.7.90). 
15. In the Seal and Rabbit (figs. VIII. XI.) there is a depressor of the first rib 
arising from the sternum. In the Seal there are, in addition, depressors of the second 
and third ribs, which are indeed, with the depressor of the first rib, additional fasci- 
culi of the external oblique (§ 67). 
16. The rectus abdominis is inserted in the Otter and Rabbit (figs. XII. XI.) into 
the first rib (§ 67). 
16 a. A depressor of the first rib, arising from the aponeurosis of the rectus, exists 
in the Dog and Calf (figs. X. IX.), and the Monkey and Ass (figs. XV. X. Archives 
of the Royal Society) (^§ 54.67). 
17. External oblique (§§ 16.26). 
17 a. In the Fowl (fig. III. a.) fibres of the external oblique arise from the sternum 
(*) 26). 
18. The internal oblique (^§ 26.54.66.93). 
19. Transversalis (§§ 11.16.26.54.60.73.94). 
19 a. In the Fowl there are sterno-costal muscles to the 1st, 2nd and 3rd ribs (§ 26). 
20. Sterno-costal muscles, or triangulares sterni (§§ 68.73.94). 
The transversales and sterno-costals combine to form one muscle in the Mammalia 
(figs. XI. b. XII. b. XIII. b. XVI. b. XXVI. Archives of the Royal Society), and in a 
modified manner in the Fowl and Chameleon (figs. III. II.) (§§ 68.73.94). 
