Electrical and Mechanical Influences. 49 



haemorrhages of course occur. Along the entire course of the 

 current tree-Hke, branching Hues of singeing (hypersemia and 

 hremorrhages), the so-called lightning pictures, may be seen in 

 the skin and intestines. In addition the blood is dark and un- 

 coagulated, the muscles dark brownish-red, the endocardium 

 stained by the altered blood, and the heart muscle at times the 

 seat of hcemorrhagic infarcts. 



Mechanical Influences. 



Pathological changes are very frequently produced by me- 

 chanical force. These are either lesions of tissue cohesion, 

 ruptures (breaks in continuity^ Icrsio continui) , or of compression, 

 as the constriction of a hollow organ, condensation of tissues 

 or displacement of organs. If this be caused by external forces 

 or foreign bodies the process is spoken of as traumatism {trauma, 

 rh rpavixa, lesiou, lat. IcTsio) . The active agent is either a dull (fall, 

 blow, jolt, pressure, pull, friction) or a pointed or sharp (stab, incis- 

 ing) solid body. In the same way internal mechanical disturbances 

 may be caused by adhesions of the tissues, tumors and other 

 pathological products producing constricting influences, or by 

 excessive blood pressure, abnormal gas expansion or pressure 

 by fluids; or may involve the functions of organs (displace- 

 ment of actively motile stomach, intestine, uterus or muscle). 

 If the force gives rise to loss of continuity amounting to visible 

 separation of the tissue the lesion is spoken of as a zvound, 

 hurt, tear (vidnus, trauma in restricted sense) ; if affect- 

 ing dense structures (as bones, cartilage or teeth), as a break 

 (fracture) ; if the tissue be destroyed by compression, as a crush, 

 contusion or bruise. Displacements (dislocations) are met in 

 joints, bones or muscles, as zvrenching or luxations; in the intes- 

 tines as ruptures (hernia), or tzvists (volvulus). The term 

 stenosis is employed in connection with constriction and oblitera- 

 tion of hollow organs ; where the closure is caused by some fac- 

 tor in the inside of the organ it is spoken of as an occlusion 

 stenosis; where it is due to external pressure it is said to be a 

 pressure stenosis. 



The results of mechanical injury are extremely numerous and 

 vary with the size and character of the producing agent, 

 as well as of the local lesion, and with the relative importance of 

 wounded tissue to the general organism. A wound is often 



