44 



NORMAL ANATOMY OF THE KNEE-JOINT. 



terval it contracted again, and slowly and gra- 

 dually recovered an action of considerable fre- 

 quency and vigour." 



" A frog was made perfectly insensible by 

 the application of laudanum or alcohol. Its 

 respiration ceased. It did not move on the 

 application of any irritant. The circulation in 

 the web was carefully observed. When it had 

 long continued in the same enfeebled state 

 without change, the thigh was crushed. The 

 circulation in the minute and capillary vessels 

 ceased at once, and never returned. The sto- 

 mach was now crushed in the same manner. 

 The heart ceased to beat for many seconds. 

 Its beat then returned, but never regained its 

 former force." 



In these experiments we have the sudden 

 influence of shock and its gradual subsidence. 

 The experiment is peculiarly interesting in 

 many points of view : 1. it is the only one on 

 record of the effects of shock induced solely 

 and cjPclusively through the medium of the 

 ganglionic system ; 2. it exemplifies the effect 

 of shock or excessive stimulus on the heart, 

 with its gradual though incomplete subsidence. 



The connexion of the ganglionic system with 

 the irritability of the visceral muscles, the 

 heart, the stomach, the intestines, &c. forms the 

 subject of an experimental investigation, in 

 which I am at this moment engaged, and the 

 results of which I purpose to give under the 

 head of vis nervosa and vis insita. It is pro- 

 bable that the ganglia are to the internal mus- 

 cular organs what the spinal marrow is to the 

 muscles of the limbs, viz. the power of irritabi- 

 lity, &.c. This inquiry is founded on a fact 

 first ascertained by myself, that, in spring, we 

 may, by portions at a time with considerable 

 intervals, totally destroy the brain and spinal 

 marrow in the frog, eel, &c. leaving the circula- 

 tion in the web or the fins and tail.* We have 

 thus isolated the ganglionic from the rest of the 

 nervous system, on which we may therefore 

 proceed to experiment, watching the effect of 

 various agents on the circulation and on the 

 action of the heart, the stomach, the intestines. 



We have thus passed in review in its anato- 

 mical, physiological, zoological, pathological, 

 and tho.se peculiar relations, the question of the 

 irritability of the muscular fibre. It only 

 remains for us to advert, once more, to the ex- 

 treme importance of this principle in physiology : 

 all physiology is involved, indeed, in the topic 

 of the nervous system and the vascular system, 

 and the principle of irritability seems, with its 

 various and appropriate stimuli, to be placed 

 between those two. 



(Marshall Hall.) 



JOINT. See ARTICULATION, and the arti- 

 cles under the headings of the several joints for 

 both the normal and abnormal anatomy. 



KIDNEY. See REN. 



KNEE-JOINT (normal anatomy of the). 

 Gr. yc'i/y ; Lat. genu; Fr. genou ; Germ. 



* Op. cit. p. 13(J. 



Kniegelenk ; Ital. ginocchio. The knee-joint, 

 the largest joint in the body, results from the 

 articulation of the os femoris with the tibia 

 below and the patella anteriorly. It admits of 

 extensive motion as a ginghmus, to which is 

 added an arthrodial motion, or a small degree of 

 rotation of the leg and foot, when the joint is 

 partly flexed. The articular surfaces are large 

 and complicated, the ligaments numerous, and 

 the joint chiefly superficial ; circumstances 

 necessary to the freedom, stability, and sym- 

 metry of the limb, but exposing this important 

 articulation to frequent accident and disease. 

 It is intended here to describe so much of, a, 

 the bones entering into the formation of this 

 joint, and, 6, the cartilages, ligaments, &c., as 

 may be necessary to the elucidation of, c, the 

 mechanical junctions. 



(a.) Bones. The shaft of the os femoris, 

 which in the middle of the thigh is triangular, 

 becomes of a four-sided form as it approaches 

 the knee, in consequence of the bifurcation of 

 the linea axpera. This rough ridge, which in 

 the middle of the bone forms a prominent pos- 

 terior angle, divides on entering its inferior third 

 into two diverging lines which terminate at the 

 convex articulating eminences called condoles; 

 a flat triangular surface of bone is thus left, 

 where the popliteal vessels lie. The outer line 

 is most strongly marked, and gives origin to the 

 vastus externus and short head of the biceps 

 flexor cruris : the inner line is deficient near 

 the upper part, over which the femoral vessels 

 pass into the ham ; it gives attachment below 

 to the vastus internus and adductor magnus. 

 The internal condyle is narrower and more pro- 

 jecting behind than the external ; and in rela- 

 tion to the shaft of the bone, it appears to extend 

 further downwards ; but the natural oblique 

 position of the os femoris brings the condyles 

 nearly horizontal. The greater width of the 

 pelvis in women gives, cateris paribus, a 

 greater obliquity to the os femoris than in men. 

 The condyles are separated behind by a deep 

 fossa, out of which the crucial ligaments take 

 their origin ; their articulating surfaces are con- 

 vex both in the transverse and in the antero- 

 posterior directions, until in front they coalesce 

 into one pulley-like surface over which the 

 patella plays in the motions of the joint : this 

 trochlea is convex from above downwards, but 

 concave from side to side ; its outer half is more 

 prominent than the inner, and extends higher 

 up the corresponding condyle. Above the 

 trochlea there is a flattened or slightly depressed 

 surface, upon which the patella partly rests 

 during complete extension of the joint. The 

 thickness of the os femoris from front to back 

 undergoes little change till the condyles sud- 

 denly jut out behind, and the edges of the 

 trochlea rise up in front ; but from side to side 

 the shaft of the bone increases in breadth as it 

 approaches the knee, the two postero-lateral 

 surfaces winding gradually round to become 

 antero-lateral, at the same time diverging ra- 

 pidly to form a smooth slope on the side of each 

 condyle. Towards the posterior part of each 

 of these sloping surfaces, there is an irregular 

 prominence called the tubcrosity,far the attach- 



