146 THE VENOMS OF CERTAIN THANATOPHIDE^E. 



oblongata) ; lungs, liver, skin, mucous membranes, the cornea, spermatozoa and 

 ciliated epithelium, and most extensively upon the mesentery and other serous 

 membranes. 



If fresh venom be injected into any organ or applied to any internal part of the 

 body, one of the chief effects is, as Dr. Weir Mitchell showed twenty-two years ago, 

 the production of minute hemorrhages. 



The studies reported here thoroughly confirm Dr. Mitchell's observations. 

 Above all, it was further evident that, as a general rule, it was everywhere the 

 parencliymatous elements of the organ or parts that underwent necrotic changes 

 {which will be described below}, while the interstitial elements of organs or tissues 

 acted upon by the venom, remained usually unaffected, or were merely infiltrated with 

 blood, or with the disintegrated products of blood. 



Effects of Venom upon Bloodvessel Walls. If fresh venom be applied to a vascular 

 tissue and watched under the microscope, no effect upon any of the larger blood- 

 vessels is perceptible. It appears that the venom even after prolonged contact has 

 no visible influence upon the smooth muscular tissue constituting the middle coat 

 of arteries and veins. The adventitia of such vessels also offer considerable 

 resistance, although the vasa vasorum become extremely congested. Even small 

 arterioles and venules are unaffected. 



The capillary bloodvessels, however, having a mere endothelial wall surrounded 

 by a delicate adventitia show a decided change upon the application of venom. 

 The endothelium constituting the capillary wall becomes cloudy and looks as if 

 roughened and displaced, and though no actual rupture of the vessel is demon- 

 strable to the eye a diapedesis of blood-corpuscles and a leakage of serum occurs, 

 and this process is sometimes ' amazingly rapid. As will be described later with 

 more details, the following are the essential points in the action of the venom upon 

 its direct application to a vascular membrane viewed under the microscope. The 

 blood current appears at first to be accelerated, and the color of the blood becomes 

 darker. Then in a few moments while the circulation still continues in the veins 

 and arteries, in many of the capillaries stagnation occurs. From these latter vessels, 

 and apparently only from them, the blood oozes, first forming pin-point ecchymoses 

 which gradually increase, and which by fusion give rise at last to a general hemor- 

 rhagic infiltration of the neighboring tissues. 



Changes in the Striped Muscular Tissues. Venom directly applied to living 

 striped muscular tissue produces changes which become apparent immediately after 

 the death of the animal. The ultimate muscular fibrilla? readily break up into their 

 sarcous elements, these becoming easily separable in transverse layers, the so-called 

 Bowman's disks. A granular change 1 of the elements, not however uniform in 

 character and distribution, is quite conspicuous. (Fig. 3.) It should be noted that 

 all these changes occur without the addition of any other reagent than venom and 

 become conspicuous when the poisoned tissue is teased out in water. 



The alterations just referred to are most manifest in muscular fibres near or 

 around which the capillaries are affected by the venom, localities apt to be marked 



1 Figured by Dr. Mitchell, in his first essay. 



