Defining Part 4 - Code cleanup toward defines (... and the rest) (#19388)

* I wasn't done

* nits

code/modules/surgery/organs/organ_external.dm

@@ -547,7 +547,7 @@ Note that amputating the affected organ does in fact remove the infection from t
 			src.transform = M
 			if(!clean)
 				// Throw limb around.
-				if(src && istype(loc,/turf))
+				if(src && isturf(loc))
 					dropped_part.throw_at(get_edge_target_turf(src,pick(GLOB.alldirs)),rand(1,3),30)
 				dir = 2
 			brute_dam = 0

code/modules/surgery/surgery.dm

@@ -468,7 +468,7 @@
  * * tool - The tool performing the operation.
  */
 /proc/spread_germs_by_incision(obj/item/organ/external/E, obj/item/tool)
-	if(!istype(E, /obj/item/organ/external))
+	if(!isorgan(E))
 		return
 
 	var/germs = 0