Archive image from page 265 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana0402todd Year: 1849 1050 THORAX. These facts show that we should be guarded in determining the living respiratory move- ments by experiments upon the dead subject. It should be constantly borne in mind, that to increase or diminish an intercostal space is to elevate or depress the ribs, and that to elevate or depress the ribs is to increase or diminish their intercostal spaces: the one cannot be accomplished without the other. Some au- thors have spoken of these as distinct; t
Archive image from page 265 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana0402todd Year: 1849 1050 THORAX. These facts show that we should be guarded in determining the living respiratory move- ments by experiments upon the dead subject. It should be constantly borne in mind, that to increase or diminish an intercostal space is to elevate or depress the ribs, and that to elevate or depress the ribs is to increase or diminish their intercostal spaces: the one cannot be accomplished without the other. Some au- thors have spoken of these as distinct; thus, that in inspiration the superior ribs ap- proximate each other, whilst they are raised, or that their rising or falling does not neces- sarily involve an increase or diminishing of the intercostal spaces ; but these two changes are simultaneous and cannot be done sepa- rately. 2nd. TJie effect of tensions, oblique, perpen- dicular, and decussating, between the moveable levers or ribs.—We employ a strip of vul- canised Indian-rubber for a force representing muscular contraction. A strip of this sub- stance, of uniform thickness, \ of an inch broad and 10 inches long, increased its length, with an increasing weight, as follows : — Fig. 686. Weight in ounces. 2 4 8 16 32 64 the pan holding the weight = 850gr. = do. do. do. do. do. do. = 1725 = 2600 = 4350 = 7850 = 14850 = 28850 Increased length of Indian rubber, gr. inches. a 1287 I H 4 Although not exactly in accordance with the law of perfect elasticity, yet it is roughly so and enough for our purpose, viz. the tension is greatest when most stretched, and weakest when least stretched, corresponding with muscular contraction. Let E E (Jig. 686.) be fixed, A B and c i>two moveable bars as before, t an oblique tension ; if t shortens, it has been supposed that the two bars would assume the position of A B' and c D ; but not so : they both rise like A B' and c D' until the two bars touch each other. If we prevent this
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