356 Tumors. 



Myomata. 



A myoma or muscle tissue tumor is composed of muscle 

 fibres, together with an accompanying vascular connective tissue. 

 Corresponding with the two varieties of muscle, these tumors 

 occur in two forms, one, the leiomyoma {myoma IccviccUulai'c), 

 composed of smooth muscle cells, and the other, rhabdomyoma 

 {myoma striocellularc) , a tumor made up of transversely striated 

 fibres. 



The latter {rhabdomyoma) is a very rare tumor; and never 

 shows the muscle tissue in a state of perfect development like 

 that of the muscles of the body. The muscle fibres are rather of 

 an embrvonic type and are usually mingled with embryonic con- 

 nective tissue {rhabdomyosarcoma, rliabdomyoma sarcomatodes) 

 or combined with glandular tissue in addition {rJiabdomyoaden- 

 osarcoma). The muscle fibres are thinner than normally, 

 ribbon shaped ; their transverse striae are not complete and are only 

 apparent along the edges of the fibres, a richly nucleated sarco- 

 plasm occupying the interior of the fibres. Numerous spindle 

 cells with longitudinal striations may be noticed in addition, 

 which may be looked upon as early stages or as muscle fibres per- 

 sisting in undeveloped condition. These muscle elements are not 

 arranged in compact parallel bundles but are scattered about in 

 irregular manner. They are therefore not of as deep red a color 

 as normal striated muscle, having rather a pale reddish-gray 

 tint. Thev occur as more or less well defined nodes ; and rarely 

 occur in situations where striated muscle tissue exists normally 

 but rather in complete heterotopism, in organs which have no 

 such basic elements. This would indicate that rhabdomyomata 

 originate in muscle germinal tissue misplaced in embryonal life. 

 This is doubtless true of the tumors in question Avhich develop 

 from the kidney, the muscular elements in their structure appa- 

 rently originating from misplaced portions of the myotomes of 

 the primitive vertebral column. Johne has recorded an adeno- 

 sarco-rhabdomyoma of this type from the kidney (hog) which 

 weighed fourteen kilograms. (In man rhabdomyomata have 

 been recognized frequently in the kidneys, testis, uterine wall, 

 urinary bladder and the oesophagus.) Besides the case above 

 mentioned, contributed by Johne, there are only two instances of 

 rhabdomyomata in animals recorded in literature (Casper). One 

 was observed by Gratia in an old horse in a dissecting room, a 

 fusiform tumor about eight or ten centimeters in length, in the 



