The examples given in the preceding section illustrate prima facie rules only. Special circumstances may bring within the class of necessaries, articles which ordinarily do not belong to it. Thus the direction of a physician to take horse-back exercise may make a horse a necessary.1 Sickness may make expensive fruits necessary.2 Expensive jewelry may be necessary as an engagement present ;3 and expensive goods furnished at a wedding may be necessaries, though they would not ordinarily be so classed.4