But as soon as we enter into further details in these cases, and especially as soon as the question affects the neighbouring areas, we find it difficult to form certain and definite ideas. We know too little of the dimensions of the various areas of vaso-motor innervation, quite too little about the different reflexes which affect the nerves of the blood vessels, and are often in doubt whether a movement acts as repleting to or depleting from a certain region. With regard to the important question of the effects of movements upon the distribution of blood in the organs of the pelvis particularly, we should be very careful in our decisions. We scarcely dare to express the opinion that a walk diminishes the quantity of blood in the pelvic organs, which we consider a certainty because the additional supply of blood flowing through the external iliac artery during the walk is greater than the additional supply in the common iliac artery, and therefore the stream in the hypogastric artery must diminish.

More detailed decisions than these are, for the present, quite unwarranted.

The Swedish gymnasts have for the most part followed Thure Brandt in their definite ideas on the effects of certain gymnastic movements upon the distribution of blood in the pelvis, especially in the sexual organs. His idea may be thus stated, that work for ilio-psoas brings blood to, work for the glutei takes blood from, the genital organs. The much used resistance exercises "knee-npdrawing" and "knee-downpressing" are considered to take blood to, "crook-half-lying knee-parting and inpress-ing," with or without pelvis-lifting, is said to take blood from, the uterus. If one remembers that the ilio-lumbar artery goes from the posterior ramus or from the main trunk of the hypogastric artery, and that the superior gluteal branch is the termination of the superior ramus of the hypogastric artery, a troublesome doubt arises as to the real connection of these things. To a philosophic mind it is good to know that this troublesome doubt never troubled either the renowned Major Brandt, who quickly but decidedly formed his ideas on clinical grounds, or other gymnasts who usually form fixed opinions in quite inscrutable ways.

But muscle work in many other ways exercises a far-reaching influence on the circulation.

The thickening of the muscle during its contraction, which is produced partly by the thickening of the muscle fibres, partly by the dilatation of the small vessels in the muscle, compresses the easily -yielding veins, both the deep veins lying between synergistic muscles and the superficial veins between the muscles and fascia, and by this means empties their blood on towards the heart, its return towards the periphery being prevented by the valves. In the same way the lengthening and thinning of the muscles following their contraction and thickening must produce an expanding effect on the compressed veins. These effects are strongest where they are most necessary. It is obvious that in the lower extremities, where the muscles correspond to 56 per cent. of the whole muscle mass of the body, the venous blood-flow must be strongly influenced by the thickening and thinning of the muscles, by which the column of blood is now squeezed, now sucked, onwards. This effect produced by the muscles is an important item in the 'mechanical series which nature has prepared to force the blood onward to the right auricle, and is a necessary part of it, working in combination with the valves of the veins, with what remains of the systolic force, either direct or due to the elasticity of the arterial walls, with the stretching of the fasciae, with the enlargement of the capacity of the veins by their expansion and its diminution by their compression during movements, with the elastic force of the lungs, especially during inspiration, and lastly with the increased pressure produced by the contraction and lowering of the diaphragm on the hepatic, splenic, and other abdominal blood vessels.

In this little reminder of the forces which assist in bringing the venous blood back to the right heart it should not be wide of the mark to draw attention to the fact that suction due to active muscular diastole does not take place in all the chambers of the heart. On the whole we can best understand the physiology of the auricles if we consider them as an expanded termination of the respective veins, and their diastole as the effect of the negative pressure which obtains in the thorax outside them, and only to a slight extent of their own elasticity. The diastole of the ventricles arises from analogous reasons; their elasticity, however, has a stronger effect. By their diastole a decided suction is exercised on the blood.

The stretching of fascia, with its influence on the circulation, is a muscular effect and must be here considered somewhat in detail, although a clear idea of these effects can only be obtained in the dissecting-room. It was Braune who showed in 1871, although the idea had already been expressed by Hyrtl, that the fasciae, along with the bones and muscles, form an apparatus which has a suction and pressure effect on the blood in the veins, working towards the centre. This apparatus varies much in its construction, but speaking generally the veins lie partly in spaces which are limited by bones and muscles and on the outer side by fascia, and which vary in volume, the space being larger when the fasciae become tense by muscular action and overcome the atmospheric pressure, but smaller when the fasciae relax and the atmospheric pressure forces them in towards the corresponding part of the body. When the fasciae become tense the somewhat flattened veins become wider, partly and chiefly owing to the negative pressure outside them due to the expansion, also owing to their being bound to the fasciae by connective tissue. The blood is therefore sucked towards the expanded portion of the vein from the adjoining peripheral part of the vein. When thereafter the fascia is relaxed in the corresponding movement and is pressed inwards by the atmospheric pressure, the expanded and hitherto somewhat cylindrical portion of vein is pressed flat and the blood is squeezed out of the region, its direction being assumed by the valves of the veins.