ILIAC ARTERIES. 



827 



venous blood. The bladder also, like the 

 heart, acquires an enormous developement of 

 its muscular coat, when any obstacle obstructs 

 the free flow of the urine from it. The physi- 

 cal condition, then, of a hypertrophous organ 

 dificTs but in degree from that of the part in 

 its normal state. There are, in general, in- 

 crease of size, of weight, and of consistence, 

 with more or less alteration of shape consequent 

 upon the former ; an increased supply of blood, 

 and a consequent heightening of colour. To 

 judge therefore how far an organ has experi- 

 enced hypertrophy, the anatomist must care- 

 fully compare its present condition, as regards 

 size, weight, colour, consistence, and supply 

 of blood, with the average state of the parts in 

 health. 



Atrophy is not only opposite in its nature to 

 hypertrophy, but it results from causes of an 

 entirely opposite kind. A defective state in 

 the nutritive process is its immediate cause : 

 the affected part shows manifest signs of wast- 

 ing ; it diminishes in size and in consistence ; 

 it loses its colour from the deficient supply of 

 blood ; its physical and vital properties are 

 manifestly altered, and are fully developed. 

 When the wasting has gone to its greatest ex- 

 tent, the natural texture disappears, or is so 

 altered as to present but few of the characters 

 of its normal condition. As frequent exercise 

 and use favour the production of hypertrophy, 

 so on the other hand disuse and inactivity 

 give rise to atrophy. Neither the vascular nor 

 the nervous systems of such parts afford their 

 wonted supplies ; and those physical characters 

 which are present in hypertrophy in an exalted 

 condition, are in atrophy either absent altoge- 

 ther, or but feebly developed. The muscles 

 of paralytic limbs, the hearts of old persons 

 which have been overloaded with fat, the 

 diminution in size and almost total disappear- 

 ance of the thymus gland in the adult, the 

 diminution of the left lobe of the liver in extra- 

 utprine life, the obliteration and conversion into 

 a fibrous cord of certain disused venous and 

 arterial canals, and the wasting of the optic 

 nerve where the eye is destroyed, are examples 

 of atrophy of every day's occurrence. (See the 

 articles on the morbid anatomy of the different 

 textures and organs.) 



(R. B. Todd.) 



ILIAC ARTERIES* (so called from their 

 situation in the iliac regions) are three upon each 

 side of the body, viz. the primitive iliac, the 

 internal and the external iliacs; they are the 

 main arteries of the pelvis and the lower ex- 

 tremity. 



PRIMITIVE ILIAC ARTERIES (common iliacs, 



* But little dissection is necessary to display the 

 iliac arteries ; the abdominal wall having been di- 

 vided and thrown back, the peritoneum may be 

 detached from without inward, along with the con- 



.tained viscus, from the iliac fossa, which having 

 been done to a sufficient extent, care being at the 

 same time taken to leave uninjured the spermatic 

 ihf vas dcfrrcns and the urclrr. the iliac 

 arteries will bo exposed still covered by their imme- 

 diate investment. 



arteritc iliaca primiliva, s. communei, 3. ftrlvi- 

 crurules; Fr. Artimiliaquei primitives; derm. 

 (ii'mintac/iuf'ttichc llnl 1-jnilr.aili in,) are two, 

 one on each side : they are vessels of great 

 size, from three-eighths to four-eight !. 

 an inch in diameter, but short, their length 

 varying from one and a half to two and a half 

 or three-quarters of an inch, the arteries being 

 longer or shorter, according to the height 

 at which the aorta divides. They arise from 

 the termination of the aorta, their origin 

 corresponding, as a mean point, to the in- 

 terval between the bodies of the fourth and 

 fifth lumbar vertebrae, and somewhat to the 

 left of the middle line of the vertebral 

 column ; the exact height of their origin, 

 however, varies considerably, ranging in ordi- 

 nary between the bodies of the third and 

 fifth vertebra ; but they have been found to 

 arise very near to the diaphragm.* From their 

 origin they descend, and at the same time in- 

 cline outward and backward, forming with each 

 other an acute angle, but more so in the male 

 than in the female subject, because of the 

 greater width of the pelvis in the latter, until 

 they reach a point ranging between the body of 

 the fifth lumbar vertebra and the sacro-iliac 

 articulalion,t where they terminate by dividing 

 into the internal and external iliacs. The point 

 of reference usually assigned for this division is 

 the sacro-iliac articulation ; but this appears not 

 to be strictly correct, the exact point varying as 

 well on the opposite sides of the same as in 

 different subjects; for the most part the division 

 takes place between the two points, which have 

 been mentioned ; at times nearer to one, at 

 times to the other, and according to Velpeau, 

 it usually occurs nearer to the spine upon the 

 right than upon the left side ; hence, according 

 to the same authority, the right external iliac 

 artery is longer than the left, and were it pos- 

 sible to ascertain these diversities of origin 

 during life, advantage would result therefrom, 

 inasmuch as the prospect of success in high 

 ligature of the external iliac must be influenced 

 by the height of its origin, and the difficulty of 

 reaching the primitive or the internal iliacs must 

 be increased in the same proportion. These 

 views appear well-founded ; the division of the 

 primitive iliac rarely takes place so far outward 

 as the sacro-iliac articulation, and for the most 

 part it is nearer to the body of the vertebra, or 

 higher upon the right than the left side, and 

 therefore the external iliac of that side is usually 

 the longer, but this disposition is not constant ; 

 the division of the right primitive artery is not 

 always higher than that of the left, nor conse- 

 quently the right external longer, and therefore 

 while probability is in favour of the conclusion 

 which the facts stated indicate, it cannot be 

 absolutely relied upon. 



The primitive iliac arteries are of the same 

 size, and nearly the same length ; the right, 

 however, is considered for the most part some- 

 what the longer, because of the situation of the 



Velpeau, who citci PeUche on the authority of 

 J. F. Meckcl. 

 t Bogros. 



