314 Mayow 



muscles attached to it externally, but in the lower 

 part it is curved outwards by the powerful Psoas 

 muscles attached internally, as is shown in Plate IV., 

 Fig. 9, in which a, a is the spine, h the muscles 

 attached externally and bending the spine inwards in 

 its upper part, c the internal Psoas muscles bending 

 it outwards. 



And I think that this cause of curvature is not 

 confined to this disease, but acts also in other cases ; 

 for if in tender age a muscle should be emaciated 

 because of any defect of nutrition, it must follow 

 that it will bend the bone to which it is attached. 



The thigh-bone and the humerus, where the muscles 

 pull equally, being attached on all sides, are rarely 

 bent to any side, being held in equilibrium : while 

 yet, as they cannot extend in length they must do 

 so in thickness, and even sometimes develop nodes. 



5. It occurs, besides, in this disease that the chest 

 is narrow and sharp : and this symptom can also 

 easily be illustrated on our hypothesis ; for the ribs 

 cannot expand their arches unless the intercostal 

 muscles are also increased, as can be seen in Plate 

 IV., Fig. ID, in which the portions of the ribs, ^, «, «, 

 a^ cannot be elongated unless the intercostal muscles 

 attached to them are similarly extended. But we 

 have assumed that the said muscles, inasmuch as 

 they are served by nerves derived from the spinal 

 marrow, cannot from defect of ahment be elongated, 

 so that the ribs cannot expand further and therefore 

 neither can the chest, but the ribs are nourished, and 

 yet, impeded by the said muscles, cannot grow in length ; 

 it follows, therefore, that they must develop nodes, 

 as they do. But this kind of growth does not corre- 

 spond to the abundance of nourishment, wherefore the 

 anterior extremities of the ribs are elongated into 



